Fullmoon Magic Crystals

Color: Light blue to blue-green
Moh’s Hardness: 7.5-8
Crystal Structure: Hexagonal
Specific Gravity: 2.65-2.75
Cleavage: None
Fracture: Conchoidal, tough

CHEMISTRY Be3Al2Si6)O18 + Fe
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.567 - 1.590
HARDNESS 7.5 - 8
SPECIFIC GRAVITY 2.66 - 2.80
CLEAVAGE Indistinct
HEAT SENSITIVE No

WEARABILITY* Excellent
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS May be heat treated to remove green tint. Very common, undetectable

Color: Green
Moh’s Hardness: 7.5-8
Specific Gravity: 2.65-2.75
Cleavage: None
Fracture: Conchoidal, tough
Crystal Structure: Hexagonal

CHEMISTRY Be3Al2Si6)O18 + Cr
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX ~ 1.57 - 1.59, varies with source.
HARDNESS 7.5 - 8
SPECIFIC GRAVITY 2.68 - 2.78
CLEAVAGE Indistinct
HEAT SENSITIVE No
WEARABILITY* Poor to Good, depending on the intergity of the gem.
SPECIAL CARE INSTRUCTIONS Emeralds usually have internal fracutres, so clean with warm or room temperature soap and water. Avoid wearing gem where it will get rough treatment.

ENHANCEMENTS Oiling, common. (Oils and epoxies are used to fill fractures, which reduces their visibility.

VALUE CONSIDERATIONS
... Like many stones, the per carat price of fine quality emerald escalates rapidly with size. For example, a recent price guide lists a fine quality, 3 carat Colombian stone as six times more valuable than three equivalent quality 1 carat stones.
... Value factors hinge largely on color with nuances of saturation and hue affecting price to a significant degree. The most desirable color is a slightly bluish green in a medium dark tone with strong to vivid saturation. Clarity is important, but inclusions are tolerated more in this variety than virtually any other gem. Top quality, unenhanced stones, (with certification,) can bring as much as 50% more in price than treated stones of the same size, color and clarity.

Color: Yellow, red, orange and brown
Moh’s Hardness: 2-2½
Specific Gravity: 1.05-1.096
Cleavage: None
Fracture: Conchoidal-brittle
Crystal structure: Amorphous

CHEMISTRY C10H160 + H2S
CRYSTALLOGRAPHY Amorphous
REFRACTIVE INDEX 1.540 (+.005 -.001)
HARDNESS 2 - 2½
SPECIFIC GRAVITY 1.05 to 1.096, usually 1.08. (Air bubbles will lower SG.)
CLEAVAGE None
HEAT SENSITIVE Very.
WEARABILITY* Good.
SPECIAL CARE INSTRUCTIONS Avoid rough handling, heat and chemicals. Amber can be attacked, (partially dissolved,) by solvents, alcohol, etc.
ENHANCEMENTS Amber is darkened by heating. If done properly, this also creates the “star spangles” effects. Amber can also be dyed to darken the color.

Amber has been in use by humans for thousands of years, possibly longer than any other gem material. It is fairly common, easy to work with and a constant wonder to the eyes.
... Amber is an amorphous mixture of organic compounds, including hydrocarbons, resins, succinic acid, and oils. Amorphous means that it has no crystalline structure. Organic refers to having its origin in living things.
... It is commonly referred to as fossilized resin of ancient conifers. However, it is not a fossil in the common sense. Most fossils begin by having an animal or plant buried in the earth. Over a period of millennia, the organic material is slowly replaced with elements from the mineral kingdom.
... Amber, on the other hand, has not had its organic elements replaced. Instead, the resin has gone through a chemical transformation. Amber has become a polymer, a natural plastic.
... This gem comes in many colors, with the most common being yellow, orange and brown. Rarely, you will find amber with a green, blue, or violet tint. This is due to extreme fluorescence.
... There are several shades of these colors and several grades of transparency. Jewelry is made almost exclusively from the transparent material. The opaque material is carved into a variety of artistic ornaments and useful utensils. Amber is also burned as incense and used as an ingredient in perfumes.
... Amber is known for its inclusions. They consist of insects, pollen and plant debris from the time the tree was living. This offers a remarkable view into the past. In some of the finer specimens, whole termite colonies are trapped. They have chambers created with webbing. Some of the "rooms" are clearly nurseries, complete with egg sacks. Besides the termites, a variety of beetles, spiders, mites, and other insects can be in a single specimen.
... Since the movie, "Jurassic Park," the most popular insect inclusion is a mosquito. However, any clearly visible insect makes a piece highly valuable. Ancient plant material is of great interest to scientists, but of little value in the jewelry market. Most of it is in small pieces and not easily recognizable for what it is.
... Another popular type of inclusion are "star spangles." These internal fractures radiate from a central point. While quite attractive, most are human induced. Hence, they do not have the high value of a good quality insect.
... Amber is often confused with copal. These are very similar materials, with nearly identical origins. The difference is that amber is millions of years old, copal just a few hundred thousand years old. There is also pressed amber, or ambroid, that is created by fusing smaller bits of amber under heat. You can distinguish this with a microscope.
... Ancient techniques for identifying amber are still useful today. Rubbed vigorously on a piece of wool, it will generate a static charge, enough to pick up a small piece of ash. When it is warm enough, it also gives off a distinctive odor. These techniques will not distinguish amber from copal, but they will separate it from plastic imitations. (They are also great for entertaining inquisitive children.)
... To distinguish between amber and copal is difficult. They share the same refractive index, specific gravity, and most other properties. Copal will fluoresce whiter than amber. That is a judgment call based on having a sufficient number of samples to recognize the difference. If you are not able to make the distinction based on fluorescence, you will have to resort to a destructive test.*
... On an inconspicuous area, place a drop of acetone. Let it sit for three seconds, then wipe it off. Copal will have the surface damaged by the acetone. Amber will show little or no change from the brief exposure.
... The easiest way to separate amber from its plastic imitations is with a specific gravity solution. A handy testing liquid can be made by boiling water and adding as much salt as you can dissolve in it. This will have a density of about 1.13. Amber, with a SG of 1.10 will float in this solution. Most of its imitations will sink.
...A few plastics are have a density as low as 1.05 and many can be lower than amber if they have air bubbles inside. So, if your sample sinks, you can be sure it is not amber. If it floats you, need to determine if it is plastic or amber.
... The RI will distinguish plastic if it varies from amber's. However, since amber and plastic can both have an RI of 1.54, it will not tell you for certain if it is amber. Since they also share so many visual characteristics, you will probably have to use a hot point to distinguish them.
...This is a destructive test, but with care, it can be done almost invisibly.* Find a place on your gem where a mark would be as unobtrusive as possible. This is usually on the bottom, an edge, or an area with existing scratches. Next, heat the tip of a needle until it glows red. Touch the selected spot just enough to release a tiny whiff of smoke.
... Now for the hard part, smell the smoke. If it is amber, the smell is of fine incense. If it is chemical and offensive, it is plastic. This is another reason to make your test on as small a scale as possible!

* Destructive tests. Practice on your own material. Ask permission before using them on a customer's gem.

Color: blue, green, yellow, pink, violet, colorless.
Moh’s Hardness: 5
Specific Gravity: 3.17-3.23
Cleavage: Poor, imperfect
Fracture: Conchoidal, brittle
Crystal Structure: Hexagonal

CHEMISTRY Ca5(PO4)3(F, OH, Cl)3
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.632 - 1.42, (variable with composition)
HARDNESS 5
SPECIFIC GRAVITY 3.10 - 3.35
CLEAVAGE Poor
HEAT SENSITIVE Yes, very.

WEARABILITY* Good
SPECIAL CARE INSTRUCTIONS Very heat senstive, clean with warm or room temperature soap and water. Avoid wearing gem where it will get rough treatment.

ENHANCEMENTS None

Value
... The major sources listing values for gems do not yet catalog the blue-green variety so I have extrapolated from the data available on the other colors. Sinkankas lists fine blue stones of between .5 to 1.5 ct at $75 to $200 per carat. His estimate for blue Brazilian stones is $100/ct. The rarest of all varieties, a rich purple from Maine, tops the list at $250 per carat.
... The degree of polish can vary on this soft stone due to skill levels of individual cutters, giving well polished stones premium value. As with most gems, saturation of color, size, and clarity are the major determiners of value.

Color: Chrysoberyl - Golden-yellow, greenish to brownish. Alexandrite - Color change from green to purple or red.
Moh’s hardness: 8.5
Specific Gravity: 3.70-3.72
Cleavage: Imperfect
Fracture: Weak, conchoidal
Crystal Structure: Orthorhombic

CHEMISTRY BeAl2O4 + Fe, Ti
CRYSTALLOGRAPHY Orthorhombic
REFRACTIVE INDEX 746 - 1.755
HARDNESS 8.5
SPECIFIC GRAVITY 3.68 - 3.80
CLEAVAGE Distinct to poor, 1 direction
HEAT SENSITIVE No
WEARABILITY Excellent
SPECIAL CARE INSTRUCTIONS None
ENHANCEMENTS None know

Alexandrite is a remarkable gem. It is one of the finest color change stones in nature, resembling fine emerald or ruby, depending on the light source. It is so rare, that most people have never seen one. Yet, when the modern list of birthstones was assembled, it was listed as June’s birthstone.
... Alexandrite has a distinguished and glamorous past. It was first discovered in the Ural Mountains of Russia in 1830. The Russian imperial colors ware red and green, so it made quite a hit. It was named after Czar Alexander II’s at his coming of age ceremony.
... The original source closed after only a few decades of mining. Today they have been reopened, but only produce a few carats a year. In 1987, a new find of alexandrite was made in Brazil. Later, alexandrite discoveries were made in Sri Lanka, Madagascar, Myanmar, and Zimbabwe. However, none of these sites produces as rich and vivid a color change as the original Russian source.

Grading Alexandrite
... Alexandrite is a color change variety of chrysoberyl. The closer the colors are to pure green and red, the higher the value. The second consideration is the amount of color change. Alexandrite can exhibit everything from 100% to just 5% color change.
... Clarity is another significant grading factor. As with most gems, the majority of what nature offers us is cabbing grade, not clean facetable material. However, with alexandrite, the color change has more effect on value than clarity. For example, say you had two gems weighing a half-carat each. One gem is eye clean, with a 50% brownish/red to greenish/blue color change. The other, an opaque cab with a 100% green to red color change, would be higher in value.
... Size is always a significant factor in value. The largest alex known is a yellow/green gem weighing 74.4 carats. The largest Russian gems are about 30 carats. However, the vast majority of alexandrites are under one carat. You can see this reflected in our Price Guide. In sizes up to one carat, top quality natural gems sell for $15,000. Over one carat, the prices range from $50,000 to $1,000,000 per carat!

Distinguishing Natural Alexandrite
... We receive many emails asking what an inherited gem is worth. Most people do not realize that there are many synthetic alexandrites and look alikes on the market. Some of these have been available nearly as long as the natural gem.
... While determining the exact origin of a gem is a matter for professionals, here is a brief guideline. If the gem has good clarity, strong color change, reasonable size, and your grandmother was not exceptionally wealthy, it is most likely a synthetic.

Color: Colorless, pink, wine-yellow and brownish.
Moh’s Hardness: 7
Specific Gravity: 3.0
Cleavage: Imperfect
Fracture: Uneven, conchoidal
Crystal Structure: Orthorhombic

CHEMISTRY CaB2Si2O2
CRYSTALLOGRAPHY Orthorhombic
REFRACTIVE INDEX 1.627 - 1.641
HARDNESS 7
SPECIFIC GRAVITY 2.07 - 3.03
CLEAVAGE Indistinct
HEAT SENSITIVE No

WEARABILITY* Excellent
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS None Known

Value Factors
... Little has been written as a guide to pricing of this gem. The International Gem Society's Price survey of Internet and standard outlets gives a range of from $20 to about $80 per carat, depending on color and size, but limits itself to small gems.
... Sinkankas and Miller in their Standard Catalog of Gem Values lists wholesale prices as between $100 - $200 per carat for larger stones. In my opinion, this is one of the rare instances of the Sinkankas book being out of sync with the present market. From my experience I would say that $20 to possibly $100 per carat is a more reasonable range for larger pieces.
... In any regard, the tried and true value factors apply to this gem very well. All other things being equal, larger, cleaner, better cut and better colored stones are worth more per carat. The only caveat here, might be that a truly colorless stone would surpass a very pale yellow, or slightly pink stone in per carat value.

Color: Red with a violet tint, red with an orange tint
Moh’s Hardness: 7.5
Specific Gravity: 3.95-4.20
Cleavage: Imperfect
Fracture: Subconchoidal, can be brittle
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron

CHEMISTRY Fe3Al2Si3O12
CRYSTALLOGRAPHY Isometric
REFRACTIVE INDEX 1.75 - 1.83
HARDNESS 7 - 7.5
SPECIFIC GRAVITY 3.95- 4.30
DISPERSION 0.024
CLEAVAGE None
HEAT SENSITIVE Some.

Color: Green yellow, copper, brown Tsavorite Garnet - Green - vanadium is the green colorant.
Moh’s Hardness: 7.5
Specific Gravity: 3.60-3.68
Cleavage: Imperfect
Fracture: Subconchoidal
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron

CHEMISTRY Ca3Al2Si3O12
CRYSTALLOGRAPHY Isometric
REFRACTIVE INDEX 1.72 - 1.80
HARDNESS 6.5 - 7.5
SPECIFIC GRAVITY 3.40- 3.70
DISPERSION 0.028
CLEAVAGE None
HEAT SENSITIVE Some.

Hydrogrossular (Garnet)

Color: Red with brown tint
Moh’s Hardness: 7.5
Specific Gravity: 3.65-3.80
Cleavage: Imperfect
Fracture: Subconchoidal
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron

CHEMISTRY Mg3Al2Si3O12
CRYSTALLOGRAPHY Isometric
REFRACTIVE INDEX 1.73 - 1.76
HARDNESS 7 - 7.5
SPECIFIC GRAVITY 3.65- 3.87
DISPERSION 0.022
CLEAVAGE None
HEAT SENSITIVE Some.

Malaia
... Malaia is a Bantu word that means out of the family, or out of the tribe. It is also used to mean prostitute or deceiver. It came into usage for a number of garnets that did not fit into any of the standard categories.

Tsavorite
... Tsavorite is named after its only source, the Tsavo Valley in Kenya. It is the chromium colored, green variety of grossular.
... These popular gems demand high value in today’s market. While faceted stones approaching 20 carats are known, their deep coloring usually keeps their size below three carats.

Hessonite
... Hessonite is from a Greek word meaning inferior. This refers to it having less hardness than other garnets.
... Hessonites are an orangish variety of grossular garnet. Sometimes their coloring leans towards the pink. Asbestos, Quebec is one of the most common sources. The miners find pinkish orange crystals among the asbestos. Africa is also a major source for hessonite.

Color Change Garnets
... Any gem that changes color is a rare find and a treat for collectors. Garnets exhibit the widest variety of color changes in the gem world, with almost every hue exhibited.
... It is commonly said that garnets come in every color of the rainbow except blue. This is still true in natural light, but there are recent discoveries of garnets that turn blue in artificial light.
... Color change garnets are mostly pyrope and spessartite in composition. Except for the color change, they are identical in properties to the Malaia variety. Their primary source is Africa.
... Idaho garnets, which are primarily almandine/pyrope mixtures, occasionally show a strong color shift from red to purplish red.

Proteus
... In Greek mythology, Proteus was a sea god, capable of changing his shape. It has become a noun for one who easily changes their appearance or principles.
... Proteus are the only treated garnets. All the others resist change, but a few almandine/pyropes from the US will change into Proteus. The treatment brings a thin layer of metals to the surface.
... This causes it to have a dual appearance. In reflected light, they have a dark gray, metallic luster, much like hematite. In transmitted light, the dark red of the garnet shows through.

Color: Orange to red brown
Moh’s Hardness: 7-7.5
Specific Gravity: 4.12-4.20
Cleavage: Imperfect
Fracture: Subconchoidal
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron

CHEMISTRY Mn3Al2Si3O12
CRYSTALLOGRAPHY Isometric
REFRACTIVE INDEX 1.79 - 1.83
HARDNESS 7 - 7.5
SPECIFIC GRAVITY 3.80- 4.25
DISPERSION 0.027
CLEAVAGE None
HEAT SENSITIVE Some.

Color: Emerald Green
Moh’s Hardness: 6.5-7
Specific Gravity: 3.77
Cleavage: Imperfect
Fracture: Subconchoidal
Crystal Structure: Isometric, rhombic, dodecahedron,icositetrahedron

CHEMISTRY Ca3Cr2Si3O12
CRYSTALLOGRAPHY Isometric
REFRACTIVE INDEX 1.74 - 1.87
HARDNESS 6.5 - 7.5
SPECIFIC GRAVITY 3.40- 3.80
DISPERSION unknown
CLEAVAGE None
HEAT SENSITIVE Some.

Color: Amethyst/Citrine mix - purple, violet to red-violet, blue/purple with yellow/gold orange
Moh’s Hardness: 7
Specific Gravity: 2.63-2.65
Cleavage: None
Fracture: Conchoidal
Crystal structure: Hexagonal

CHEMISTRY SiO2
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.544 - 1.553
HARDNESS 7
SPECIFIC GRAVITY 2.651
CLEAVAGE None
HEAT SENSITIVE No

WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS None known.

Quartz which occurs in bands of yellow and purple has been given the name of ametrine (amethyst + citrine). Originally discovered in Brazil, the world's current supply comes from one area in Bolivia. The crystals from this mine often exhibit an abrupt color transition, which probably reflects dramatic changes in temperature during their formation. Much citrine today is produced by heating amethyst, so it is easy to imagine natural heating and/or cooling occurring in such a way as to produce the bicolored quartz. Clarity and good size make it a favored material of gem carvers and cabochon artists as well.
... Quartz, at hardness 7 with no cleavages, make good jewelry gems, although daily wear in rings will result in eventual dulling of the polish. No special care is required as they are not sensitive to temperature change or household chemicals.
... Both heat enhanced natural quartz, and synthetic ametrine are on the market and as they are optically and physically like Nature's product, sophisticated gemological testing is necessary to detect them.
... Initially cutters favored windowed emerald shapes with a 50/50 split of colors, and much of the rough is still cut this way. More recently, however; some cutters have begun to cut a variety of shapes, many of which create internal reflections that blend the yellow and purple into attractive shades of rosy gold and mauve, or create mosaic-like flashes of both yellow and purple.

Value Factors
... The value of ametrine is rather modest. Like most quartz gems it is often found in fairly large, clean pieces, so the per carat price increase larger sizes does not occur. The major value point to be considered in the material itself is the depth and vividness of the colors and in many cases how distinct the separation is.
... Much of the value in many pieces comes from the artistry of the cutting or carving. There is a world of difference to be seen in a commercial grade or native emerald cut, and a fine custom stone, even from the same material.

Color: Purple, violet to red-violet, blue/purple
Moh’s Hardness: 7
Specific Gravity: 2.63-2.65
Cleavage: None
Fracture: Conchoidal
Crystal structure: Hexagonal

CHEMISTRY SiO2
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.544 - 1.553
HARDNESS 7
SPECIFIC GRAVITY 2.651
CLEAVAGE None
HEAT SENSITIVE No

WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS None

Crystalline quartz in colors ranging from pale lilac to deep reddish purple and ranging from transparent to translucent is known as amethyst. Siberian mines once produced the world's finest stones with particularly rich purple color that glowed with reddish and/or bluish highlights. Today the term Siberian no longer is a place designation as the mines are long since worked out, but instead is used a a "grade" term, implying colors similar to the original stones from Siberia.
...Today's major sources are Brazil, Bolivia and Uruguay in South America and Zambia in Africa. Brazilian stones can be found in huge sizes, but generally are moderate in color. They often suffer from color-banding, which sometimes is visible despite efforts of the cutter to minimize it.
...Many amethyst lovers prefer the usually smaller, but more richly colored stones coming from Zambia and, more recently, from Uruguay.
...Very light amethyst which once was considered low grade, has gained a recent boost in popularity by intensive marketing on TV shopping programs and the clever marketing strategy of calling it "Rose de France". To my mind these light stones have their greatest appeal when given fancy and unusual cuts, where the artistry of cutting is more on display than the material itself.
...At hardness 7 and with no particular warnings on care necessary, amethyst makes a fine jewelry gem for all purposes. Lower grades of material are cabbed, carved, and made into a great variety of beads and other ornamental objects.

Color: Orange, orange/red, yellow, gold, brown/orange
Moh’s Hardness: 7
Specific Gravity: 2.63-2.65
Cleavage: None
Fracture: Conchoidal
Crystal structure: Hexagonal

CHEMISTRY SiO2
CRYSTALLOGRAPHY Hexagonal
REFRACTIVE INDEX 1.544 - 1.553
HARDNESS 7
SPECIFIC GRAVITY 2.651
CLEAVAGE None
HEAT SENSITIVE No

WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS one

ENHANCEMENTS Amethyst can be heat treated to change it to citrine. Not common. "Madeira" Citrine" with red flashes is a result of heat treatment.

Value
... At the top end of the scale are prime specimens of the most saturated yellows, oranges and reddish tones. Those with less intense color fall into lower value ranges with pale or smoky stones at the bottom. As with any gem material custom cutting increases value and inclusions decrease it. There is no exponential increase in value per carat with increase in size as larger sizes are readily available. In many fancy cut or carved specimens, the majority of the value is due to the artistry of the fashioning.

WEARABILITY* Excellent
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS May be dyed.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on "Hardness and Wearability."

WEARABILITY* Very Good
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS Can be heat treated to improve color. Rarely done.

Value
... Sinkankas places a wholesale value on small, commercial quality faceted stones at around $40 per carat for clean gems with good color. Larger stones and those with custom cuts fetch up to $200 per carat. Federman doesn't give an exact price range, but suggests that, next to other gemstones one might find in good jewelry, they are "reasonable".

WEARABILITY* Excellent
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS May be dyed.

Agate

...Agate is distinguished by having multiple colors. While not usually as rich as our crystalline gems, the colors can be quite vivid. Agates are sometimes opaque, but they are frequently translucent, and occasionally completely transparent.

Banded Agates
... Banded agates are some of the most popular. They are found all around the world, with Brazil being one of the most productive sources. Note that many of the richly colored, banded agates you see for sale are dyed.

Lace Agate
... Lace agate is noted for its delicate designs.
Mexico is one of the premier sources for this
material.

Dendritic, Moss and Plume Agates
... These agates have in common that they contain mineral inclusions which may be any color, but share a roughly tree-like or branching form (dendron = tree). Those which have a more plant or feather-like appearance have been called moss or plume agates, respectively. All agates take a wonderful polish and are tough enough for most jewelry uses. Designers often take advantage of the intriguing patterns these stones have to offer.

Picture Stones
Some of the most treasured gems are those that show a picture that appears to be taken from nature. Oregon's Biggs Jasper is now the most common source. Bruneau Jasper, from Bruneau Canyon, Idaho, used to be the preferred material. Gems from this locality frequently had blue "skies" which the Oregon material lacks. Unfortunately, a dam has submerged the mining site and the material is now quite rare.

Value
In general, agate prices are quite modest with most of the price paying for the fashioning rather than the material itself. In the case of these agates, those with particularly distinctive or landscape like patterns, or those of especially large size, are at a premium. Sinkankas lists wholesale values of commercial grade standard cabs as ranging from $.50 - $20 each, depending on size. Custom cutting or pieces from collectible locations would be substantially more expensive. Especially fine patterns are cited as bringing up to $200 per piece.

Fire Agate
... My appreciation for fire agate has taken time to reach its current high level. Most of the pieces I saw early on were poorly fashioned and of low quality, and frankly, I was not impressed. Since starting this web site, however, I have had the opportunity to see some outstanding specimens and, as a result, my enthusiasm has increased dramatically. Fire agate is a brown, microcrystalline quartz which has a botryoidal, (grape-like,) growth form. It contains layers of plate-like crystals of iron oxide, (limonite,) in various planes within it. The iridescent colors of red, gold, green and rarely, blue-violet, result from interference between light rays traveling through these thin layers. (We see the same effect when looking at the rainbow colors at the surface of an oily puddle of water; or in the "orient" created by the layers of nacre on the surface of pearl.)
... Usually, fire agate pockets occur within specimens of colorless, white, or light gray chalcedony. Fire agate is found only in the American Southwest and Mexico and was not brought into commerce until after World War II. This, combined with the fact that it is one of the most difficult cab materials to cut properly, keeps it scarce and mostly unknown to the general public.
... In order to best reveal the colors, the overlying layers of chalcedony must be removed from the botryoidal surface creating a freeform shape with a carved upper surface. Such treatment requires substantially more time per piece and tends to elevate cost. This type of fashioning also leads to a lack of calibrated pieces and has prevented the use of this gem in mass produced jewelry items. Good fire agates are as impressive in their color-play as fine black opal, but far less expensive. Additionally, fire agate is as hard and durable as any quartz making it wonderful for jewelry uses, including rings. The colors and form are rich and dramatic and generally appeal strongly to men (although I can personally attest to their appeal to women!)

Value
... The most desirable pieces show color over the entire surface with no dead spots. Red color is the most highly valued, but the few pieces with a sort of lavender-blue are also sought after. Federman lists the wholesale value of the most desirable pieces at a maximum of $20-$25 per carat.

Jasper
... Jasper is an opaque, solid or patterned variety of cryptocrystalline quartz which consists of very tiny quartz crystals colored by various mineral impurities. The names of various jaspers can come from their color: bloodstone, green, lemon; from their pattern: orbicular, poppy, leopardskin, landscape, Picasso; or from a place name: Morrisonite, Mookite.
... All types take an excellent polish, are trouble free to care for, and hardy enough for all jewelry uses. These stones are usually cabbed, sometimes carved, and seldom faceted.
... Jewelry use of jaspers goes back into the early history of civilization. Various forms of this material are also frequently made into decorative objects, such as ashtrays or bookends. Jaspers are found all over the world, with certain colors or patterns unique to particular locales. Most bloodstone comes from India, all Mookaite from Australia.

Value
... Jaspers, in general, are very common; hence most of the value in a given piece relates to the saturation of its color, the beauty of its pattern or the artistry with which it is fashioned. Some types such as Imperial Jasper and Madagascar Jasper do command premium prices as they are relatively rare. In rock shops, pieces of commercial quality cut in simple shapes might be had for $5 or less. Fine material, cut in designer forms, generally ranges between $2 and $5 per carat.

Tigers Eye
... Crocidolite, (blue asbestos,) alters to quartz, but while retaining its fibrous structure. This material is frequently stained by iron, giving it a golden brown color. We know this material as tigers eye. Unstained pieces, retaining their original blue color, are called Hawks Eye. There are also pieces with both colors.

Chalcedony
... In this description, chalcedony will mean any translucent, cryptocrystalline quartz with a single color, whether it has a special variety name or not. The various types differ in color due to metallic impurities, such as iron, nickel, copper, and titanium present during crystallization. This group of stones is usually cabbed or carved, although an exceptional, near transparent piece may be faceted. Chalcedonies are tough gems, good for all jewelry applications and require no special care in wearing or cleaning.

Carnelian
... The best-known and generally least expensive variety in this group is carnelian. It ranges in color from yellow-orange to rich, near reddish orange, to orangey brown, and varies from semi-opaque to highly translucent. Carnelian is the only type of chalcedony which is regularly enhanced. Iron is the source of its color and as a result it can be easily heat treated, (even by the sun's heat alone,) to darken red tones as the iron is oxidized. You should assume, unless informed otherwise, that any piece of carnelian has been enhanced in this way. Most commercial carnelian comes from India, but it is mined world wide.

Chrysoprase
... Apple green chalcedony that derives its color from nickel is chrysoprase. Ranging from nearly opaque to nearly transparent, its color spectrum includes olivey, to nearly pure greens of medium tone. Very fine, highly saturated pieces have been successfully misrepresented as Imperial jade. Most chrysoprase sold today comes from Australia. Prase is a darker, less saturated form, rarely seen, which comes from Eastern Europe. There are also very small amounts of a green chalcedony colored by chromium found in Africa, called Mtorolite.

Chrysocolla Chalcedony
... Marketed as "Gem Silica" this relatively rare, blue to blue-green, opaque to near transparent material is the most expensive type of chalcedony. Found almost exclusively in Arizona its color is due to copper. Those who take the trouble to seek it out and are willing to pay the price are rewarded with a glorious color, (elsewhere found only in the soft gem Chrysocolla,) in a stone that has the durability and hardness of quartz.
...

Blue Chalcedony
... This material is the darling of today's gem carvers and jewelry designers. Piece after piece is featured in magazines like Lapidary Journal, Modern Jeweler, Metalsmith and Ornament. One look at the ethereal colors in this group will tell you why.
... The various blues, each group of which has its vocal supporters, are generally designated by place names. They vary in depth of blue color and degree to which the blue is modified by gray or pink hues. As a group, they vary from pale to medium tones and in degree of translucency.
... Some pieces have a slight adularescence that enhances their value. This phenomenon, which reaches its apex in moonstone, is due to light interference from layers of microscopic inclusions and looks like a shimmering, floating, interior light. Mohave and Mt. Airy Blues originate in California and Nevada, respectively and are slightly to moderately grayish blue with a light to medium color range. Blue chalcedony from Namibia, often called African Blue, varies from grayish to nearly pure blue and from light to medium dark. The most unusual type, and arguably the most valuable, is from Oregon. Its blues are modified by slight to moderate amounts of pink, making a noticeably lavender gem, which nonetheless is called "Holly Blue."

Value
... General high value points for all chalcedonies would be strong color saturation and high translucence. Sinkankas in his Standard Catalog of Gem Values, 2nd. Edition, and Federman in his Modern Jeweler columns discuss some price ranges for various high grade chalcedonies. Chrysoprase from $10-$30 per carat in finest grades, Gem Silica from $12-$50 per carat and blue chalcedony from $10 to $100 per piece. The IGS, (International Gem Society,) market price survey lists $10/ct as the going price for blues. Carnelian is common enough that its value is more a function of the beauty of the cutting than the material itself.

Other Chalcedonys
... Turritella agate is composed mostly of turritella shells, embedded in agate.
... Iris agate shows iridescent colors reflecting from between the color layers.
... Sard is similar to carnelian, but with a brownish tone and more opaque.
... Prase is a green, or yellowish green chalcedony.
... Plasma is a dark green, opaque variety. It frequently has white or yellowish spots.
... Bloodstone, or heliotrope, is plasma with red and orange spots of iron oxide.
... Onyx is a chalcedony with straight bands of colors. Black onyx occurs in nature in thin bands. What you find in the stores is almost always dyed.
... Sardonyx is onyx with white and red layers.
... Flint and chert are opaque, dull gray or white. They rarely make an appearance as gems, but are useful materials for arrowheads, driveways, and other utilitarian purposes.
... Petrified wood and dinosaur bone are primarily chalcedony in their modern composition. The lapidary will cut and polish them like any other quartz family gem.

WEARABILITY* Good
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS None know

VALUE
... Charoite is a gemstone bargain. Even the highest quality pieces are, at most, a few dollars a carat. Look for a lovely pattern, pleasing colors, a good polish and a shape that appeals to you, and you cannot go wrong. If the piece shows some chatoyancy, that would add to its value.

WEARABILITY* Excellent
SPECIAL CARE INSTRUCTIONS None

ENHANCEMENTS Some colors produced by irridation, common. Laser drilled to remove inclusions, common. Cracks filled with glass, occassional.

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DIAMOND GRADING
...Diamonds are graded on four qualities, commonly known as the 4 C’s.

COLOR
CLARITY
CUT
CARAT

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COLOR

...The closer a diamond is to being colorless, the greater it’s value. When the current grading system was introduced in the 1930’s, diamonds were commonly called grade A, B, or C. So the current system began color grading with the letter D, to avoid any confusion.
... Colors D, E and F are the highest grades. They are described as “near colorless.”
... Colors G, H, I and J come next. They are described as “white.”
... The colors from K to Z are tinted, (usually yellow or yellowish brown.) Those that are just lightly tinted, K, L and M are often said to “set white.” That means that they are so lightly tinted that they will appear white if set in yellow gold. You would however notice their color if set in white gold or platinum.
... As one gets further down the alphabet, the tinting gets stronger and the value lower. That is, until you get to the extreme. As the color becomes richer, you have a fancy colored diamond, rather than an off colored one. Then the value starts going up again.
... Color grading is done by placing a diamond next to a set of previously graded gems. The color is compared to the graded gems to see which it comes closest to matching.
... While this low tech approach is accurate, it is also expensive and time consuming. A compromise is often made on smaller gems, by grading batches within a range, rather than coming up with a specific grade. You will usually find diamonds under a carat graded as GH, or IJ, meaning that they are in that range.
... This information is meaningful and saves you quite a bit of money. It costs over $100 to accurately grade a diamond. If you have a large diamond, where subtle differences in quality grades make a significant difference in price, then it is worth while. However, that isn’t cost effective for the majority of gems.

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CLARITY

...The clarity of a diamond is determined by the size and number of inclusions inside of it. An inclusion can be another mineral, a fracture or occasionally a void. Simply put, it is anything that will interfere with the free passage of light.
... Just like with color, there are many clarity grades. They are judged by what an expert can see at 10 power magnification, under ideal conditions. The highest grade a diamond can get is Flawless. That means no inclusions can be seen at 10 power magnification. It does not mean inclusions can’t be found with higher magnification, nor should you assume it is the only grade with no inclusions visible to the naked eye.
... Clarity grades use the letters V, S and I. They stand for Very, Small, and Inclusion. Progressing from Flawless, the grades are VVSI1, (Very, Very Small Inclusions One,) VVSI2, VSI1, VSI2, SI1 then SI2. These are the grades of diamonds that have no “eye visible” inclusions, those that can’t be seen with the naked eye. (Note, some SI2 stones will have small, eye visible inclusions.)
... As we progress down the grading scale, there is I1 and I2. These have eye visible inclusions, but are still considered to be gem grade.
... Then there is P1 and P2. They are not usually considered gem grade because so little light will pass through them. However, since they have the magic name diamond, they do show up on the market regularly.
... Beware of ads “1 carat diamond ring, $299.” Just because something is a diamond, doesn’t mean it is a gem. In fact, the vast majority of diamonds mined are usually considered “industrial grade” and are used as abrasives. Many of these "industrial grade diamonds," those graded as P1 and P2, find their way into jewelry simply because they had the advertising appeal of being diamonds.

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CUT

...This one of the hardest properties to judge, plus there are a number of factors to consider. The first one has to do with the brilliance of the gem.
... The pavilion facets of the gem are intended to act as mirrors, to reflect the light entering the stone, back towards the observer. However, the angle they are cut at has a lot to do with how efficiently they work. Note: If you are unfamiliar with this terminology, see our article on “Gem Cutting Terms.")
... The ideal angle for diamond pavilion facets is 41 degrees. This is usually quite convenient, based on the shape of a standard diamond crystal. Unfortunately, not all mined diamonds are in excellent proportions. The diamond cutter is often faced with having to compromise between maximum brilliance and maximum yield. The economics are such that, if the cutter removes too much material from the original crystal, there is no profit in it. Hence, many diamonds get cut at less than ideal proportions.
... Diamonds have a high refractive index, which gives them their great brilliance. A little cheating here or there is insignificant. However, if the cutter varies a little further from the ideal the brilliance begins to suffer. Still more and you get a gem that just doesn’t stand up to others in terms of brilliance or fire.
... There are no standards for this. Most jewelers are familiar with correct proportions and can judge it from the shape. The best test for most of us is to simply compare the gems side by side. If you have two diamonds of the same grade and one is significantly brighter than the other, the cut is the difference.
... Please understand that the above discussion assumes we are talking about round diamonds. Because of their symmetrical proportions, all the major facets can be cut at the same angle. The same does not hold true for other shapes.
... Many people prefer a marquis shape. This is fine, but do not expect a marquis, or any other shape, to be as brilliant as a round. On a marquis it is necessary to cut a number of facets to accommodate the shape. The angles these facets get cut at vary, slightly to greatly, from those that give the greatest brilliance. This is a simple fact of physics: the more facets that are cut at the ideal angle, the greater the brilliance of the gem.
... When looking for diamonds you may come across the terms, "Single Cut,” “Old Mine Cut” or “European Cut.” These are gems that only have eight facets running from the girdle down and eight up to the table. That makes a total of 17 facets. A standard round brilliant cut has 57 facets.
...These “single cuts” are usually used on small accent stones, but occasionally you will find an older diamond of decent size with this cutting. Obviously, these gems won’t have the brilliance of a full cut diamond, therefore they aren’t worth as much.
... Another factor that comes under the heading of cut have to do with the shape of the gem. An ideal cut gem should be symmetrical, not lop sided. This point should be obvious, but sometimes it is helpful to point it out. A misproportioned gem can be camouflaged in it’s setting and you might not notice it until you have paid for it. This may not bother you, but it might lead to dissapointment.
... Though hard, diamonds are also somewhat brittle. (If this doesn’t make sense to you, see the article on Hardness and Wearability.) The girdle of the gem is the widest part when viewed from the top and the thinnest when viewed from the side. If cut too thin, it can present a weak area that is just asking for trouble. These illustrations will give you an idea of what normal proportions are. Some girdles get cut to a knife edge and this is definitely something to be avoided.

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CARAT

...This is by far the easiest of the factors to understand. Simply put, smaller diamonds are more common than large ones. Therefore smaller diamonds cost less per carat than large ones.
... If you were to see a diamond broker's price list, under each grade, the price per carat would go up with size. A grade of diamond that would cost $900 per carat in the ½ carat size might cost $1100 per carat at ¾ of a carat and $4000 in a full carat.

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CHOOSING A DIAMOND
... You should spend six months income on an engagement ring. I know that, I heard it on television! For a salesman that is a great idea. However, picking a diamond is something much more personal than finances.
... Economics vary from person to person and family to family. I wouldn’t presume to advise you on how much you can afford, but I can help you wade through the morass of grading information and put it in common language.
... As a rule, I suggest diamonds that are in the white range of color, (G, H, I or J,) and those with clarity grades SI1 or SI2. Visually these are wonderful diamonds. They are bright and lively they will dazzle all your friends!
... You might consider a lower grade of color if the right deal was presented to you. An L graded diamond can look white in a yellow gold setting and be quite brilliant. The fact that it costs less per size might be worth your while. I wouldn’t recommend looking for this grade, but if you found one in a setting that you really love it would be worth serious consideration.
... Going down in clarity grading can occasionally be worth your while too, depending on the individual diamond and setting. Sometimes the “eye visible” inclusion that got it that ranking is insignificant and the overall appearance is still delightful.
... Going down further in quality is rarely worth while. I know a lot of jewelers make their living by supposedly underselling the competition, when in fact they are selling lower grade gems. Without better quality diamonds near by to compare with, the customer is often convinced they are getting a great deal. The diamonds sparkle, the price and terms are just, oh, so sweet!
... The disappointment comes later. Imagine your fiancé showing off her engagement ring, (something they usually get great joy out of,) only to find hers is dull compared to those of her friends. You no longer have a great deal. The enjoyment of the diamond goes way down when you compare a lower quality gem to a good one.
... Please consider this factor carefully! While choosing a diamond is a personal thing and not everyone will have the same opinion, most folks will get more enjoyment from a higher quality dazzler, than a larger but mediocre gem.
... How about going up in quality? That is a personal matter. If you get an emotional boost from owning the biggest and the best and can afford it, then you certainly should. However, for most people who simply want a fine gem on their finger, it isn't necessary.
... People who are serious about their diamonds and get to look at a lot of them, get a real joy out of finding those rare gems that are nearly colorless or nearly clean under magnification. These gems are much rarer and therefore demand a higher price. But that does not mean they are much prettier, nor does it mean that you will get more enjoyment out of them.
... If you were to set two well cut diamonds side by side, one graded D, VVSI1 and the other G, SI1, you would see very little, if any, difference with the naked eye. You would have a strong emotional reaction when you heard the prices though!
... The point is simple, these are the rarest quality gems and the difference is only apparent to the sophisticated diamond appraiser who inspects them carefully with magnification.
... There is occasionally a difference between a diamond graded SI1 and SI2. (SI1 is defined as “small inclusions, somewhat easy to find.” SI2 is defined as “small inclusions easy to find.”) When I look at a gem graded SI1 I usually see something like the first illustration. One or two tiny dark spots that have no effect on the brilliance of the gem.
... Those graded SI2 have inclusions placed near the center where they are more visible, or many more of them. Some gems graded SI2, like the first illustration, will have no significant difference in brilliance. In an extreme case, where there are many inclusions, (even though none are large enough to be seen without magnification,) they may make up 5% or more of the visible area. That means a 5% or more reduction in brilliance.
... One of the most important elements of a diamond's appearance is the cut. This is a difficult element to judge. Diamonds are rarely cut to ideal proportions, but they have such high optical properties that most of them are still beautiful. Without getting overly technical, you can judge the quality of cutting by simply comparing diamonds side by side. Look for overall brilliance and fire; those little flashes of color. If the diamond you are considering does not have the sparkle of the other gems, then keep looking.
... To summarize, it is usually best to go with quality rather than size, but if your budget is limited the rarest qualities may not be worth your money.