Amethyst
Amethyst is a violet to purple variety of quartz. It gets its color from gamma irradiation and the presence of traces of iron in its crystal lattice. The irradiation causes the iron atoms to lose an electron and form a color center. The color is not evenly distributed in the crystals, and it is often most intense in the growth zones under the rhombohedral faces. In some crystals, the color appears in phantom-like thin layers. The iron content in amethyst is relatively low, in the 10-100 ppm range.
When heated to more than about 300-400°C, amethyst loses its violet color and often turns yellow, orange or brown. It may also turn colorless or rarely green. With excessive heat, amethyst will turn into citrine. Prolonged exposure to sunlight will also slowly fade amethyst. Lapis Lazuli |
The name lapis lazuli comes from the Latin words for "stone" and "blue" and has been used for centuries as a gemstone and a pigment. It was one of the most important gemstones in ancient Egypt, and it was also used by the ancient Greeks and Romans. It is found in only a few places in the world, the most important being the Sar-i-Sang mines in Afghanistan which has been producing lapis lazuli for over 6,000 years.
Lapis lazuli is a type of rock that is made up of three minerals: lazurite, calcite, and pyrite. Lazurite is the blue mineral that gives lapis lazuli its color. Calcite is a white mineral, and pyrite is a gold-colored mineral. It is also a felspathoid, which means that it is similar to feldspar. It is cubic in shape, has a hardness of 5.5, and a specific gravity of 2.7 to 2.9. It has a vitreous to greasy luster. |
Mother-of-Pearl
Mother-of-pearl is the iridescent layer that forms on the inside of a shell. It is made up of layers of aragonite, a type of calcium carbonate. The iridescence is caused by the way light reflects off of the layers of aragonite. It comes in a variety of colors, including white, gray, silver, yellow, blue-green, bronze, pink, red, brown, black, and banded.
Here are some of the common color combinations that appear in mother-of-pearl:
Mother-of-pearl is a beautiful and versatile material that has been used for centuries by cultures around the world. |
Shattuckite
Shattuckite is said to have metaphysical properties, such as promoting peace and tranquility. Mainly found in the Southwestern United States, including Arizona, Nevada, and New Mexico, it can be found in Mexico and other parts of the world. It is a copper silicate mineral so technically it is not a gem. Typically found in reniform, globular, botryoidal, and stalactitical formations, it is a translucent stone that can be polished to a glassy shine. With a Mohs hardness of 3.5, it is considered a soft stone.
It is typically blue in color, ranging from turquoise to deep royal blue. It can also have striations, mottling, webbing, or other patterns. Although rare, some specimens have a blue streak. Since shattuckite is often a pseudomorph of other minerals, it can also be found in other colors, such as red, brown, white, or green. Turquoise |
Turquoise comes in many colors, but most often green and blue. It is a hydrated copper and aluminum phosphate, and is typically opaque. The most valuable turquoise specimens are those with a spider web matrix.
In the United States turquoise can be found in Arizona, Colorado, New Mexico, and Nevada. The stones found in these locations contain impurities that form matrix streaks within the stone. However, turquoise is becoming more rare as mines begin to be played out. Turquoise is formed as a secondary mineral through a process known as hydrothermal replacement. This occurs when chemicals leach out of nearby rock and deposit in cracks or veins. Copper eroding from deposits and combining with phosphates is another aspect of the turquoise formation process. White turquoise is not found in nature due to the physical properties of the mineral. However, a gemstone called White Buffalo is found in similar areas. It is pure white with black spider web inclusions, but is not considered to be turquoise. Moss AgateMoss agate is a gemstone that looks like moss with many of the same colors and patterns. The colors can range from sea green to dark forest green. The moss-like patterns are actually made of minerals, such as manganese or iron.
Moss agate is often found in pieces of weathered volcanic rock and is a type of chalcedony, which is a type of quartz. It’s not a traditional agate, because it doesn’t have the same banding that traditional agates have. Brown moss agate is rare. |
Fairburn Agate
Fairburn Agates are among the most prized stones from North America. These richly colored fortification agates are distinctive, rare, and sometimes valuable, which makes them a staple in the collection of rockhounds in North America.
Fairburn Agates are a specific variety of banded chalcedony that show up in South Dakota and Nebraska. Like all agates, they’re comprised of silica and impurities that give them colors, along with the distinctive banding that gives the family of stones their name. These agates are quite rare, and great specimens are even rarer. For that reason, they aren’t popular as jewelry stones, and even tumbling can sometimes be considered destructive. Instead, the majority of them end up as specimen pieces with either one face polished or just a bit of cleaning depending on the surface consistency of the individual stone. |