Da Yooper's Guide to
Isle Royale Greenstone, ( Chlorastrolite ) a variety of Pumpellyite, Ca2(Al,Mg,Fe)3(SiO4)3(OH) * H2O, a Michigan mineral closely related to the epidote family, was named after Isle Royale, the island in Lake Superior on which they can be found. Good quality Greenstones are considered Semi-precious Gemstones of rare beauty. This Copper Country Mineral was officially named the Michigan State Gem in 1972 and the gem is slowly gaining in popularity outside it's area of renown. Principly because few gems can equal a high quality Isle Royale Greenstone for sheer beauty.
Chlorastrolite (Green star light), a form of Pumpellyite, when polished, has a beautiful chatoyance (see greenstone on left) or play of light on the crystaline structures in the stone. Greenstones are relatively abundant, (except in gem quality) and can have salmon, pink, green, red, black and white inclusions and will occur rarely with 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 $10.00.
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.
Very Large Greenstones For Sale
#4 44mm X 14mm in Matrix $700.00
Da Yooper's Prospecting, Metal Detector Buffs, Rockhounds, Fossil Hunters, Treasure Hunters, and All Lapidary Friends a place to swap Stories, Locations, Field Trips, Information, Finds, Methods and Friendship.
"Da Yooper's Rockhound & Lapidary Auction", is the ideal place to buy and sell your unwanted finds and to add to your collections. Rocks, Minerals, Fossils, Crystals, Jewelry, Artifacts, Collectibles and other Finds may be posted.
Back ground image is of Isle Royale as seen from Great Sand Bay
Below are some unusual Greenstones
Da Yooper's Quiz
throughtout the world, nowhere on earth is it found in
such purity and abundance as in Michigan. What mineral is
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
Da Yooper's Links
Chlorastrolite by Gerald Collegnon
Da Yooper has
other Gem Quality Greenstones available for sale. Please email
Da Yooper with your requirements.