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.
Heulandite is a zeolite mineral named for Johann Heinrich "John Henry" Heuland. Crystals are often bladed with a pearly luster.
Hickoryite is a red, pink, and yellow banded variety of Rhyolite that comes from Rodeo, State of Durango, Mexico. Autumn or rainbow hickoryite is mostly brown or tan with red, pink, or yellow bands.
Hiddenite is the green chromium-rich variety of spodumene, which is rarer than its pink sibling, kunzite. Hiddenite is named for American gemologist William Hidden, who first discovered this transparent green variety in North Carolina in the area that now also bears its name, Hiddenite.
Natural animal horns have been used for both practical purposes and adornment for millennia. Horn is distinctively beautiful with natural earthy to golden and one-of-a-kind color variations. Its soft nature lends to ornate carving.
Not well known to the general public, howlite is one of those minerals that is almost more famous for imitating another mineral. In this case, the other mineral is turquoise, a phosphate gemstone. Howlite is naturally milky white in color and often has dark vein-like mineral inclusions. Because of its porosity, it accepts dye fairly easily, achieving a turquoise-like blue color. Howlite accepts a nice polish and its porcelain-like luster is appealing.
Hydroxyapophyllite crystals are tabular and are frequently striated. It is typically colorless or white, but can be pink, light green, pale yellow, blue, brown, or violet. The mineral can be found in Jefferson, NC and Kimberley, South Africa.
Hypersthene is a common mineral in the pyroxene group that rarely forms distinct crystals. Hypersthene is similar in appearance to hornblende, but it is a harder material. Since the hardness difference was the main way to tell the stones apart the Greek words “hyper” meaning above and “stenos” meaning power gave the inspiration for the name. It is usually brown, green, or gray with vitreous to pearly luster and displays a brilliant coppery metallic surface sheen.
Idocrase, also known as vesuvianite after its discovery at Mount Vesuvius, has crystals that are prismatic and glassy. It is usually green or chartreuse in color, but may be found in yellow to brown, yellow-green, red, black, blue or purple hues.
Ilvaite is name after the “Ilva” the Latin name for the island of Elba, Italy. It is black and forms in prismatic columns or large masses of indistinguishable crystals.
Indicolite is one of the most valuable and collectible of all elbaite tourmalines, with hues spanning from lighter to deep, intense blues. Cutting indicolite can be a task for even the most skilled of cutters, as it is strongly pleochroic and appears darker when viewed down the crystal. This factor must be taken into consideration when cutting, as a loss of transparency and brilliance can occur in darker specimens.
Inesite is part of the triclinic crystal system. It typically has pink spindly crystals that radiate out in fan like clusters. The mineral gets its name from the Greek word for “flesh fibers” due to its appearance. It is a late-stage hydrothermal mineral found in manganese deposits.
Iolite is the gem-quality blue or blue-violet variety of cordierite. While iolite enjoyed popularity in jewelry in 18th-century Europe, this naturally beautiful gemstone is relatively new to today's jewelry market, and is regaining popularity with the public. Because of its varying levels of hardness and strong pleochroism, iolite is one of the most difficult stones for lapidaries to fashion. It must be cut in certain directions to take advantage of the best color, which can be tough when the shape of the rough doesn't lend itself to cutting in that same direction.
Ivory has long been treasured for its beautiful white color and ability to be finely carved. As opposed to bone or horn, ivory is derived from the teeth and tusks of animals. Because of the devastating impact of poaching due to the ivory trade, the importation and sale of such materials is severely restricted or banned in many countries.
The term jade is used for jadeite and nephrite jade. For centuries the two materials were considered one and the same. It was not until 1863 that they were identified as different minerals with a similar appearance and properties. Jadeite jade is a member of the pyroxene group and is primarily composed of the mineral jadeite. Nephrite is a tough rock comprised of intergrown crystals of minerals from the tremolite-actinolite solid solution series, part of the amphibole group.
Jade has been treasured for some 7,000 years for its unique luster, lovely color and impeccable toughness. This precious gem has always had special significance in many Asian cultures, and can be compared to the West's admiration of diamonds and gold. For centuries, nephrite jade and jadeite were considered one and the same. It was not until 1863 that they were identified as different minerals with a similar appearance and properties.
Jasper is an opaque, fine grained variety of chalcedony quartz. It is typically found in red, yellow, brown or green colors and is generally spotted with these colors. Its name comes from the Latin word for the gem, iaspis, meaning "spotted stone."
Jeremejevite was named for a Russian mineralogist in 1883, but there are rarely any specimens found in Russia today. Recently Namibia has started to produce some mentionable crystals, but in such small amounts the stone is still very rare. Jeremejevite is typically found in pale blue-green, cornflower-blue to yellowish brown hues.