Elements
Emerald Emerald is one of the most well-known and desired colored gems known to mankind. There is evidence of emeralds being mined and used in jewelry going back to over 3,500 years before present. It is a variety of the gem beryl, colored green by minute traces of chromium, vanadium or both. While emerald has a hardness of 7.5-8 on the Mohs scale, it is typically very included, which limits its toughness. To increase the clarity and durability of the gems, nearly all emeralds are filled with either clear resins or oils. This means that special care should be taken when cleaning emeralds. Named Species/Varieties There are no named varieties or species of Emerald. Where is it found Emerald is found in a number of localities in the world. However, the largest deposits mined today are in Colombia and Zambia. The Colombian emeralds are widely regarded as the finest in the world due to their high chromium content and relatively high clarity for emerald. In the United States there are minor deposits of emerald in North Carolina. In recent years there has been several finds of fine emeralds in Ethiopia, as well as some finds of lighter green emeralds in Nigeria. Untreated emerald is extremely rare and valuable. Because emeralds are almost always filled with cracks and fissures when they come out of the ground, they are typically filled with resins or oils to improve the clarity and stability of the stones. These resins should be colorless, but occasionally colored resins are used to falsely enhance the color of the gems. While oils like cedar oil were commonly used in the past, in recent decades this has largely been replaced by specialized resins that are more durable, and closely match the refractive index of the emerald, giving the gem a better overall appearance. Even though treatment is common in emerald, it should still *always* be disclosed to the buyer. Use in jewelry Very few jewels are as popular in jewelry as emerald. While relatively hard, the internal fissures reduce the toughness of the gem. As a result, it should be treated with care, particularly when cleaning it. That said, it’s hard enough to be used in any type of jewelry, and is particularly popular in rings.
Amethyst Amethyst is the purple variety of the common rock crystal, or quartz. It’s been known and used as a gemstone since antiquity. The ancient Greeks and Romans thought that it could help prevent drunkenness, and wore jewelry made of amethyst or drank from vessels carved from amethyst. The color of amethyst can range from a very light violet-pink (“Rose de France”) to a very deep purple. The finest amethyst will show flashes of red and blue in a traditionally faceted stone; deep purple amethyst with this effect can be quite valuable as it is relatively rare. Where is it found Amethyst is found in a wide variety of locations around the world. The most significant economic deposits are in Brazil, Uruguay and Zambia. Siberia historically has produced some very fine deep purple amethyst. In the US, Georgia has produced some remarkable gem-grade amethyst and the Four Peaks region of Arizona is famous for its deep-colored amethyst deposits. Amethyst is typically untreated. However, it can occasionally be heated to lighten the color slightly, or to turn it into the more rare and valuable ametrine.Use in jewelryBecause it is relatively common and has good hardness (7 on the Mohs scale), amethyst is very popular in jewelry. Gems can often be found in larger sizes and are used in carvings as well as traditional faceted gems.
Aquamarine Aquamarine is the blue-green to blue gem variety of the of the mineral beryl. It’s been known and used as a gemstone since antiquity. The color of aquamarine can range from a very pale blue-green to a deep strong blue (“Santa Maria” blue is some of the finest blue aquamarine known); the value increases with the depth of saturation of the color, and as it shifts from a more greenish blue to a purer blue hue. Aquamarine is typically quite clean, and flawless larger gems are not uncommon. That said, large gems in the finest colors are quite rare. Named Species/Varieties There are several types of aquamarine named after particular locales. For example, very fine deep blue gem aquamarine was found in Santa Maria de Itabira, Brazil in the 1950’s. It became so well known that many deep blue aquas are referred to as “Santa Maria” aquamarine, although the name is also used for lesser quality material in an attempt to justify a higher price. Another variety is “Maxixe” beryl; it turns a beautiful deep blue when irradiated, but will fade to a pale color with exposure to daylight. Beryl can also be found with parallel growth tubes that create a “cats-eye” chatoyancy effect when properly oriented and polished. Where is it found Aquamarine is found in a wide variety of locations around the world. The most significant economic deposits are in Brazil, Nigeria and Mozambique, however, it can be found in literally dozens of countries around the world. In the US, gem aquamarine has been found in Maine, New Hampshire and Connecticut, as well as Pennsylvania, North Carolina and Georgia on the east coast. In the western US it can be found in Colorado, Wyoming, Idaho and California. Treatments Aquamarine is often heated at low temperatures to reduce the greenish cast and increase the blue hue. This can be difficult to impossible to detect, and hence has no impact on pricing. Some aquamarine may also be irradiated and heated in an attempt to improve the color. Use in jewelry Because it is relatively common and has good hardness (7.5-8 on the Mohs scale), aquamarine is very popular in jewelry. Gems can often be found in larger sizes and are used in carvings and fantasy cuts as well as traditional faceted gems.
Tourmaline Tourmaline is a remarkable gemstone, coming in an incredible variety of colors. Tourmaline can also be found in multi-colored forms, which is relatively uncommon in gemstones. It is actually a family of minerals that share a similar chemical structure. Most gem tourmalines are of the elbaite type, although certain dravite and liddicoatite tourmalines are also used as gems. It has been used as a gemstone for many hundreds if not thousands of years, but only in the past three centuries or so has it become a prominent gem variety highly sought after for use in jewelry. With a Mohs hardness of 7.0-7.5, its a relatively durable gemstone and suitable for use in a variety of jewelry. Tourmaline is highly pleochroic, often showing two completely different colors on the different optical axes of the crystal. While this can create a beautiful visual effect in many gemstones, some color combinations do not blend well, and careful orientation of the rough when cutting is crucial to getting the best color in a finished gemstone. Named Species/Varieties There a number of named varieties of tourmaline: Rubellite for red to reddish-purple tourmalines, Indicolite for blue to blue-green tourmaline and verdelite for green tourmaline. Watermelon tourmaline is red to reddish-purple with a green rind, similar to the watermelon fruit. Tourmaline colored by trace amounts of copper was first discovered in Paraíba State, Brazil and the term “Paraíba-type” is now used for all copper-bearing tourmaline. Tourmaline in almost every color can be found as chatoyant “cats-eye” gemstones. Where is it found? Tourmaline is found in wide variety of locales around the world. Major economic deposits are found in the United States (historically in Maine and California), Brazil, Nigeria, Mozambique, Madagascar and Kenya to name a few. Treatments Tourmaline may be subjected to a variety of treatments to improve the color or stability of the material. It is often heated to lighten up darker colors, or change the color. For example, purple copper-bearing tourmalines can be heated to a bright blue-green hue that is very desirable. It can also be irradiated to change the color. Pale pinks can be turned a deep rich magenta or red with irradiation and then heating to anneal the color. Finally, some tourmaline is treated with polymers or oils to improve the clarity, as some varieties of tourmaline are prone to cracks fissure-like inclusions. Use in jewelry The brilliance, wide range of colors and hardness of tourmaline make it a great choice for use in jewelry.
Rhodolite Rhodolite is the name used for gem garnets that are a pinkish red to purple-red color. It is composed of two of the end species of garnet in roughly equal proportions–almandine and pyrope. Iron is responsible for giving rhodolite the lovely ranges of reds to purple-reds that fine rhodolites are prized for. Rhodolites can have inclusions of fine rutile needles (these inclusions are referred to as “silk” and can give the garnet a soft glow in the hand that is difficult to capture in a photo) or tiny internal crystals of zircon and other minerals. Generally the best gems are eye clean. Rhodolite can often be found in larger sizes, but as they get larger they can become dark. Rhodolite garnets have excellence brilliance due in part to a high refractive index of 1.760. With a Mohs hardness of 7-7.5, rhodolite is a durable gemstone. Named Species/Varieties There are a number of regionally-named varieties of rhodolite garnet. One of the most well-known is Umbalite, a more purple-magenta variety found in the Umba River Valley of Tanzania. Recently some remarkable purple garnets have been found in Mozambique and been marketed as “Grape Garnets” or “Purple Garnets,” although they are simply a very purple variety of rhodolite.Where is it foundThe first gem-grade rhodolites were found in North Carolina, and given the name in honor of the similarly-colored rhododendron flowers native that region. Gem grade rhodolites today are mostly mine in Africa, with significant deposits in Kenya and Tanzania. It is also found in Sri Lanka, Nigeria and a few other localities around the world. Treatments Rhodolite is not treated. Use in jewelry The brilliance and hardness of rhodolite make a great choice for jewelry, especially given the popularity of red-colored gemstones in general.