Gemopedia

Ranging from green to brownish black in color, gadolinite is a mineral that counts Russia as one of its primary sources. Interestingly, gadolinite is prized for the two rare earth elements it contains: yttrium and cerium.

Galena is found as attractive mineral specimens. Its cubic structure with perfect 90-degree cleavage planes along with its bright silver like metallic luster is eye catching. Most galena is mined as a lead ore. Argentiferous Galena is sought after for its silver content and greatly increases its ore value.

Though they all have the same crystal structure (cubic, like diamond and spinel), garnet is an entire group of minerals that vary in their chemical composition, resulting in a variety of gems featuring different colors and properties. Though some varieties of red garnet are common and found on nearly every continent on Earth, other garnets like orange spessartite, green demantoid and tsavorite, are much less abundant. There are more than 20 garnet species, but the five most important include pyrope and almandite (the combination of which creates rhodolite), spessartite, grossularite or grossularite (which includes hessonite and tsavorite), and andradite (which includes demantoid). Garnets of all species are the birthstone for January, so January babies aren't limited to the well-known red varieties.

A bright grass-green to olive or yellowish green gemstone first discovered in Canada. Gaspéite is commonly used to carved into artistic sculptures. This stone can be faceted or cut as cabochons and set in jewelry.

Gadolinium gallium garnet, thankfully abbreviated to GGG, is a man-made diamond simulant that entered the market in the 1960's. Today it is rarely used as a gemstone, and is instead manufactured for optical and industrial uses. The Czochralski method of gem synthesis involves the melting of various elements in a platinum crucible. A small gem crystal (called a seed) and attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed. For this reason, the Czochralski method is also known as crystal pulling. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.

Gadolinium gallium garnet, thankfully abbreviated to GGG, is a man-made diamond simulant that entered the market in the 1960's. Today it is rarely used as a gemstone, and is instead manufactured for optical and industrial uses. The Czochralski method of gem synthesis involves the melting of various elements in a platinum crucible. A small gem crystal (called a seed) and attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed. For this reason, the Czochralski method is also known as crystal pulling. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.

Glass has been used for thousands of years as a decoration. It is sometimes employed as a gemstone simulant, but is often appreciated entirely upon its own merits, especially when formed with a high level of artistry.

Goldenite comes in white and black varieties coated with a patterned gold layer. The black stones are hornblende a common natural rock composed primarily of iron, magnesium, potassium, and calcium. The white stones are white quartzite, a rock made up of interlocking quartz grains.

Goldstone is glass that contains myriad of tiny angular crystals of copper. First made in Italy, goldstone forms by reduction of particles of copper oxide within the glass during a process called annealing. Nothing in nature looks quite like glittering goldstone. Made in three distinct colors (blue, green and orange), goldstone is a tough and durable material that can be made in large pieces and fashioned into slices and objects of almost any desired size and configuration.

While most members of the beryl family such as emerald or aquamarine are famous for their colors, goshenite is the highly collectible colorless variety that displays a diamond-like fiery brilliance. Interestingly, pure beryl is colorless, with traces of different metallic elements being responsible for this gem family's great color range. Always limited in availability, goshenite is named for the locale where it was first discovered--Goshen, Massachusetts.

Grandidierite is a greenish blue or bluish green mineral named after French explorer and naturalist Alfred Grandidier. The mineral was originally discovered on the southern coast of Madagascar in the Andrahomana area. A new gem quality deposit was found near Tranomaro, Madagascar in 2014.

The first grossular garnet specimens discovered were pale green and similar in color to the gooseberry. This species of garnet gets its name from the Latin name for gooseberry "Grossularia". Not all grossular garnets are green. Most grossular garnets are better known by their variety names hessonite, tsavorite, mint, leuco garnet, and hydrogrossular.

Gypsum is a mineral that has been utilized since antiquity. This soft mineral represents the second level on the Mohs hardness scale. Cut stones are rare because gypsum has perfect cleavage, and it is too soft to facet. The fine-grained variety known as alabaster is used for carvings and decorative objects. Selenite is the large crystalline variety that is popular with mineral collectors. The fibrous variety is known as satin spar. Gypsum sometimes crystallizes in rosette patterns known as desert roses. Gypsum is probably best known for its use in construction materials like sheetrock, cement, and plaster.

Discovered in Greenland in the late 1890's, hackmanite is named for Finnish geologist Victor Hackman. It is a rare occurrence to find gem-grade hackmanite; at best, most crystals are translucent. Hackmanite is the light pink to pale violet variety of sodalite. It is a particularly unusual gem because it exhibits a special optical property known as "tenebrescence," a type of reversible photochromism. This feature allows the gems to temporarily change color when exposed to different light forms. While hackmanite gems are usually pink to violet, the color quickly fades to gray or greenish-white in sunlight, and will slowly return to the original color after changing the light. Its tenebrescent property makes hackmanite a prized mineral for collectors.

Hambergite is an often colorless gemstone named in honor of Swedish mineralogist A. Hamberg. While it is durable enough to wear in jewelry, hambergite is most commonly seen in specimen form. Rarely is a specimen flawless, and it can be easily confused with colorless quartz since they are similar in appearance. A unique characteristic of hambergite is its prefect cleavage that makes faceting into a gemstone very difficult for cutters.

Hausmannite is a brown to black mineral that is part of the spinel group. It was named after Johann Friedrich Ludwig Hausmann who was a professor of mineralogy at the University of Göttingen in Germany. Some of the finest samples come from Namibia and South Africa.

Haüyne is an extremely rare mineral and even rarer gemstone. Its bright blue color is common for this stone, but it can be found in white, gray, yellow, green, and pink colors too. Lazurite the sulfur rich variety of haüyne is what gives lapis lazuli its blue color. The best-known specimens have been found in Eifel Mountains of Germany.

Also known as Mount St. Helens stone, helenite is a man-made stone that originates from the ashes of the Washington State Mount St. Helens eruption in 1980. While the volcanic ash was being removed, it was discovered that it contained glass particles that turned a beautiful green color when heated. This glass is commonly made and fashioned into jewels that may be green, red or blue.

Displaying characteristic yellow to orangish yellow and greenish yellow, heliodor is the most cheerful variety of beryl. Interestingly, as an allochromatic gem, pure beryl is colorless, with traces of different elements responsible for beryl's wide range of colors. Heliodor is named from ancient Greek words meaning "gift from the sun," as it was once believed that heliodor harnessed the power and warmth of the sun and was responsible for the change between day and night.

Hematine is a hematite simulant sometimes called hemalyke, hemalike, or magnetic hematite. It was originally reported to be pressed and sintered iron oxide, but most material currently on the market is a ceramic-like material composed of barium-strontium ferrite. Hematine is highly magnetic, whereas hematite is not.

Hematite is a dark gray to black mineral known to various cultures throughout history. Babylonians, Egyptians, Greeks, and Romans were a few of the civilizations that made use of this mineral. Hematite derives its name from a Greek word for blood, an allusion to the reddish powder produced during the fashioning process due to the presence of iron.

Found in several worldwide locations that are often zinc-rich environments, most hemimorphite crystals are white to grayish white, yellowish or totally colorless. But when the robin's egg blue hues are found, miners know they have hit a pocket of true gem-quality material. Not only is fine quality hemimorphite geologically scarce, but there are few locations that have the right combination of trace minerals that create this stunning blue color. This gem is often appreciated as natural specimens due to its almost bubbly botryoidal crystal habit.

Herderite is a rare collector’s gem, typically found in smaller sizes. This mineral occurs in green, bluish green, white, colorless, yellowish, or gray. Herderite was first discovered in Germany in 1828, but Brazil is today's dominant source. Collectors treasure herderite for cyclic and “fishtail” twinned crystals. Some specimens exhibit phosphorescence when exposed to X-rays.

Nicknamed the "cinnamon stone", hessonite is a variety of grossular garnet and the color ranges from golden yellow to brownish orange or brownish red, as well as reddish orange to red. A perfectly colored hessonite is a bright golden orange that resembles a combination of honey and orange with an internal fire. Some hessonites have tints of brownish red that resembles the color of cinnamon. Hessonite can be found in the gem gravels of Sri Lanka, but it is also found in Brazil, Canada, Italy, Myanmar, Russia, and the United States. While the clearest gems are the most prized, inclusions in hessonite are common, and often give stones an oily or roiled appearance.