AFRICAN TURQUOISE Not turquoise at all, African “turquoise” is actually a type of jasper found in Africa. It is typically dyed to achieve the color that looks like traditional turquoise. The natural matrix is what helps it mimic turquoise so well. African turquoise jasper is harder on the Mohs scale than turquoise, making it a good substitute when the customer wants a less fragile, more affordable option. This stone is often sold simply as “African turquoise” which is a misleading misnomer and it should always be clarified that this stone is jasper.
AGATE Agate, like jasper, is a variety of chalcedony. The difference being that agate is semitransparent, while jasper is opaque. Agate is also banded, meaning color appears in stripes, or bands. There are many, many, types of agate. It is sometimes dyed different colors. Moss and dendritic agate are two types that are not “true” agate, since they aren’t banded, but are called so because they contain multiple colors. Green hornblende inclusions give the mossy appearance in moss agate, and dendritic agate has tree- or fern-like inclusions.
- MOSS AGATE and MOSS QUARTZ describe a quartz-variety mineral with moss-like inclusions. It tends to be called agate when the matrix is opaque or semitranslucent, and quartz when the matrix is transparent colorless. Moss agate is not “true” agate, since it isn’t banded, but it is called so because it contains multiple colors. Green hornblende inclusions give the mossy appearance in moss agate. Despite its name, moss agate/quartz does not contain organic material. It is usually formed in weathered volcanic rocks.
AMAZONITE Amazonite, named for the Amazon River, is a variety of feldspar. Interestingly, it is thought it was named because of green stones that were once found near the Amazon River, although feldspar doesn’t exist in the Amazon at all. The name may also be a nod to the lush green rainforest. While copper is usually the source of green and blue color in stones, it is thought that in amazonite, tiny quantities of lead and water give the color. It is not typically treated in any way.
AMETHYST Amethyst is a variety of quartz. It is abundant and a much-loved stone, due to its vibrant purple color. It has long been a top choice of royalty, and was once believe to ward off drunkenness! The color of amethyst can be the result of heat treatment. Amethyst can also be heated to become prasiolite (green), citrine (yellow), or smokey quartz (gray/brown). Prasiolite is often incorrectly referred to as “green amethyst.” Amethyst is the birthstone for February.
- MOSS AMETHYST Moss amethyst is complicated term, generally referring to quartz or amethyst with inclusions that may include goethite or hematite. Some clear quartz specimens with goethite or hematite inclusions may erroneously be called “leipdocrocite” – see lepidocrocite entry for more information. Another material sometimes called “moss amethyst” is also known as “cacoxenite amethyst.” This is the term used for amethyst with suspected cacoxenite inclusions. These inclusions are said to appear as gold or brown needles. However, some believe it is impossible for the mineral cacoxenite to grow within quartz, and that the inclusions are goethite. In the metaphysical world, this material, when thought to include the following seven minerals -amethyst, clear quartz, smoky quartz, cacoxenite, rutile, goethite, and lepidocrocite – is called “Super Seven” or “Melody’s Stone.” However, it is unlikely that cacoxenite is included, and nearly impossible, if possible at all, for the mineral lepidocrocite to be included within quartz. Therefore, we can just appreciate these stones with inclusions for the mystery of what’s within.
- CAPE AMETHYST Cape amethyst is the name for a stone containing both purple amethyst and milky quartz.
ANDALUSITE Andalusite is not very well known, mostly because gem-quality andalusite is rare so it hasn’t had the chance to be widely loved. It comes in many colors and is strongly pleochroic – in large enough stones, a color change can be seen when viewing from different angles. Almost all gem-quality andalusite comes from Brazil. It is very rarely subjected to any treatments, although heating for color improvement is known to occur.
APATITE The name “apatite” comes from the Greek apatein, which means deceiving – because it is often mistaken for other minerals. The bones and teeth of most animals, including humans, are made of calcium phosphate, which is the same material as apatite. Some specimens are fluorescent – they light up orange under certain lighting conditions. There are three types of apatite, and most apatite is fluorapatite. It has been found in meteorites. Apatite is generally untreated, but some blues may be enhanced with heat treatment.
AQUAMARINE Aquamarine is a blue variety of beryl, the same mineral as emerald and morganite. The name comes from the Latin words for “water of the sea.” The best specimens are totally transparent and eye-clean. Many of the aquamarines used as gemstones are heat treated to improve their color, this helps eliminate unwanted green tones. Sky blue is considered the most desirable hue for this stone. Aquamarine crystals can form different structures, including a six-sided hexagon or can even take the form of druzy. Aquamarine was once a “sailor’s stone,” believed to protect sailor’s from rough seas and storms. The US Navy even named a ship the USS Aquamarine during WWII! Some major producers of aquamarine are Brazil, China, Pakistan, Burma, and even the US. It is the Colorado state gemstone. Aquamarine is the birthstone for March.
- MOSS AQUAMARINE Moss aquamarine is a type of beryl, just like classic aquamarine. The moss variety contains trace iron, which lends itself to the moss-like internal characteristics. Though it is considered to be simply low-grade aquamarine, because of its color and inclusions, these characteristics have actually made it a desired and much-loved stone.
AVENTURINE Aventurine is a form of quartz. It often has a shimmery effect, caused by platy mineral inclusions. This effect is called aventurescence. Most commonly, aventurine is green, but it can be other colors. The name comes from the Italian a ventura, which means “by chance,” alluding to the discovery of aventurine glass or goldstone. Sunstone may be called “aventurine feldspar” although aventurine and feldspar are different and sunstone is truly a feldspar. Aventurine may be dyed to change the color.
AZURITE Azurite is named for its “azure blue” color. It has been used historically as a pigment, although it doesn’t make a very good one because it is unstable in air. It is possible for azurite to undergo chemical changes and become altered to malachite, while retaining its’ original crystal structure. Azurite is generally not treated in any way.
CARNELIAN Carnelian is a variety of the mineral chalcedony, brownish-red to orange in color, and translucent to semi-translucent. Carnelian is very similar to, but also different from, sard, which is generally accepted as more brown. It’s also similar to jasper, but jasper is always opaque and exhibits multiple colors. Carnelian has been used as a gemstone since ancient times - the first known faceted carnelian dates to 5000 BC. It is sometimes heat-treated for color, and rarely, it is dyed.
CHALCEDONY Chalcedony is a microcrystalline variety of the mineral quartz. It is translucent to opaque and can be almost any color, but naturally it is often white-to-blue, bluish-gray, or brown-to-black. Many well-known stones such as agate, jasper, carnelian, and onyx, are actually types of chalcedony. Chalcedony has been used by people since at least 1800BC. It holds dye fairly well, and the bright colors of chalcedony, as well as the ever-popular aqua chalcedony, are the result of this treatment. It can be heated to create carnelian. When dyed green it is called green onyx.
CHAROITE Charoite is a unique gem that is easily identified because it isn’t like anything else. What we call charoite is a rock, meaning it is composed of multiple minerals, one of which is the mineral charoite. This is what gives the signature purple color. It often has dark or black swirls or patches. The other minerals include pale greenish gray microcline feldspar, greenish-black aegirine-augite, and orange tinaksite. Sometimes called “lilac stone,” it was discovered in the 1940s in Russia, near the Chara River, which remains its only source. Charoite may be dyed.
CHROME DIOPSIDE Until recently, chrome diopside was really only a collector’s gemstone. Now it has become mainstream, used more commonly in jewelry. It has an intense green hue that can be compared with emerald, but it isn’t as hard as emerald. As the name implies, chrome diopside gets its’ color from chromium. Two notable locations where chrome diopside is mined are Pakistan and Siberia (where it was discovered in 1988). It is not treated in any way.
CHRYSOCOLLA Chrysocolla gets its cyan/blue/green color from copper – it contains the copper hydroxide mineral speriniite. Otherwise, its’ structure has been questioned, although sometimes it grows with quartz or contains chalcedony. Chrysocolla can rate anywhere from 2-7 on the Mohs scale – a huge range, due to varying silica content. It is often confused for turquoise due to its’ color. It is not typically treated.
- CHRYSOCOLLA CHALCEDONY Chrysocolla chalcedony, also known as chrysocolla-in-chalcedony, or gem silica, is very rare. It is not actually chrysocolla, rather it is chalcedony colored by the same copper salts that give chrysocolla its bluish-green color.
CHRYSOPRASE Chrysoprase is a variety of chalcedony colored by nickel impurities. Much of chrysoprase is natural, but occasionally white chalcedony can be dyed to imitate chrysoprase. It can grow as solid green or with banding. About 85% of the world’s chrysoprase comes from Australia. It is not typically treated.
CITRINE Citrine is a variety of quartz that occurs rarely in nature. It often grows with amethyst, and when found together the resulting stone is called ametrine. Most of the citrine available on the market is actually heated amethyst. Untreated citrine generally has a paler color. The name “citrine” comes from the French word “citron,” which means lemon. Citrine has been valued for centuries.
CUBIC ZIRCONIA Cubic zirconia is a man-made substitute for diamond. It is extra sparkly and can be totally colorless – an extreme rarity for diamonds. It can be “doped” with many elements to create a variety of colors, though colorless is the most popular. It is the cubic crystalline form of zirconium dioxide, which is where it gets its name. This is a different material from zircon, a natural mineral. The natural form of CZ was discovered in 1892 and is called baddeleyite, but it is never used in jewelry. CZ is a popular alternative to diamond, not just for looks and price, but because many want to avoid purchasing a “blood diamond” or contributing to conflicts related to diamond mining.
EMERALD Emerald is a variety of beryl, like morganite and aquamarine. It is one of 4 precious gemstones, along with ruby, sapphire, and diamond. Cleopatra was known for her passion for emeralds. The first known emerald mines were in Egypt, dating to 330 BC. The name emerald has been used frequently throughout history to describe lush landscapes and rich greens. Flawless emerald is very rare and emerald is often treasured for its’ “flaws.” It can be oiled, dyed, or irradiated to address the characteristic flaws, and these are industry accepted practices.
EUDIALYTE Eudialyte (sometimes called eudalite) was discovered in 1819 in Greenland. Today, much of the eudialyte on the market comes from the Kola Peninsula, Russia. It is also found in Brazil, Canada, Norway, and has been found in Arkansas. Its’ name means “well decomposable,” which alludes to its solubility in acid. It is a relatively rare stones, easily identifiable by its pink / red / magenta coloring. It is not typically treated.
Much of the information in this post came from my personal knowledge. I also used www.Mindat.org, www.Gemdat.org, www.Geology.com, www.Minerals.net, Wikipedia, and of course www.GIA.edu. I recommend all of these sources as reliable and trustworthy.