Billion year old American Garnets
Crystal Specimens, Rough Gem Material and Cut Stones
Garnet is a semi-precious gemstone found around the world. One of the hardest minerals available, garnet has been a favorite gemstone across time as it is today, and is also used an industrial abrasive for sandpaper, glass polishing and other industrial purposes, with Mohs hardness of 7-8 (higher than quartz). Garnet is a group of minerals with slightly different chemistries and similar crystal structure. Our garnets are found as intact trapezoihedron (24sided) crystals, in layers of soft, mica-rich soil.
Star Garnets are a rare form of the garnet crystal. The “star” quality or “asterism” is created from minute rods of rutile (TiO2) titanium oxide crystals, that form inclusions within the gemstone, oriented to reflect light from inside the stone. Star Garnet was designated the official Idaho state stone in 1967. More rare and precious than either star rubies or star sapphires, the Idaho garnet is usually dark purple or plum in color, with four-rays in the star typically, but rare six-rays (as in a sapphire) are occasionally found in Idaho.
Idaho is known as "The Gemstone State" with mountains containing veins of gold, silver, lead, zinc, cobalt, copper, and many other rare minerals including the star garnet, jasper, opal, jade, topaz, zircon, and tourmaline. Idaho is one of only two locations in the world to produce 6-ray star garnets, the other being Sri Lanka.
USFS Emerald Creek Garnet Area
Geology and Mineralogy - The deep pinkish-red, pyrope/almandine garnet in the Bechtel Butte / Emerald Creek area of Idaho occurs in layers of soft mica schist, of the Pre-Cambrian Belt Supergroup, a billion years old. Garnet crystals are concentrated in pelitic/shale intervals of pre-Cambrian age meta-sediments, which were subject to high temperature, amphobolite-grade regional metamorphism and strong tectonic forces near one billion years ago.
Regional metamorphism of the ancient sedimentary package by later tectonic activity was enhanced again with proximity to the Idaho Batholith, a quartz-rich, molten, granite intrusion of Cretaceous age (50-100 mya) which increased the temperature and recrystalization of the meta-sediments.
Professional experts agree that this mine contains the “mother load” of the upper Wallace Formation of the Belt Supergroup, one of only two deposits of 6-ray Star Garnets in the world (the other in Sri Lanka), because it is located along the axis of a strong syncline, with the finest material yet uncovered.
Placer garnet deposits including rare star-garnets, are well known in the Wallace Fm. north of the Idaho Batholith, where soft soils are easily eroded and heavy, garnet crystals collect at the bottom of stream deposits.
"West Pine Gallery is a wholesale supplier
of pre-Cambrian Idaho Garnets, jewelry and art work,
Mailing address: P.O. Box 69, Boulder, Wyoming 82923