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| Formula: Ca2(Al,Mg,Fe)3(SiO4)3(OH) * H2O System: Monoclinic Lustre: Vitreous Color: Green, Blue Hardness: 5.5 Streak: White Michigan's State Gem Isle Royale Greenstone ( Chlorastrolite ) is a variety of the mineral Pumpellyite. Ca2(Al,Mg,Fe)3(SiO4)3(OH) * H2O is a mineral closely related to the epidote family, that was named after Isle Royale, the island in Lake Superior on which they can often be found. Isle Royale Greenstones is considered a semi-precious gemstone of rare beauty. Officially named the Michigan State Gem in 1972, the gem is slowly gaining in popularity outside it's area of renown. Few gems can equal a high quality Isle Royale Greenstone for sheer beauty. Chlorastrolite (Green star light), another name for Isle Royale Greenstone is a form of Pumpellyite and when polished, has a beautiful chatoyance or play of light on the crystaline structures in the stone. Relatively abundant, (except in gem quality) it can have pink, green, red, black and white inclusions and more rarely inclusions of copper and silver. Greenstones are found in the waters and on the shores of Isle Royale (hence the name) and in some areas of the Michigan Copper ranges of Lake Superior. Many of the old tailings of the mining era have Greenstones in them. Look for the dark green, small round or almond shape nodules in the poor rock. The problem of course is getting them out of the rock without damaging them. Sometimes they will have weathered out of the rock and can be found lying on the ground. You will find after all the hard work, that only a small percentage are greenstones, as most will be chloride, prehnite or some other mix of minerals. And of course, of all the greenstones found, perhaps 2 or 3 out of a hundred will be gem quality. Greenstone specimen as a rule, are quite small. A pea-sized stone can be considered a nice specimen. Greenstone larger than this possessing a good pattern are extremely rare and hard to find. You may order a Greenstone Specimen (Approximately 5mm) with a discription of Greenstone from Da Yooper for $8.00. In the tourist shops of Copper Harbor, MI, the best jewelry quality greenstones are valued at up to $200.00 per carat and are in high demand by jewelers and collectors. Greenstone Jewelry is fast becoming popular, and the demand far exceeds the supply.
Da Yooper's Quiz Rare
throughtout the world, nowhere on earth is it found in
such purity and abundance as in Michigan. What mineral is
it? Green
Stones are sometimes called Turtle back stones. Michigan
has another famous stone sometimes called a Turtle back
stone. What is it? What is the name of
a small Pink, White and Green semi-precious stone found
in Michigan's U.P.? |
Rough
Click above for enlarged image and Identification of Rough tumbled Amygdaloidal Basalt before sorting for Isle Royale Greenstone.
Beautiful Greenstone & Copper Slab
Example of Greenstone Jewelry
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Index Current Auctions Chlorastrolite by Gerald Collegnon |
