Jades From Other Perspectives
Jade Perspectives
Dark Blue Jadeite from Guatemala
We are starting this category and post to stimulate viable conversations concerning both Nephrite and Jadeite, from professionals and amateurs alike, of differing perspectives of both “Jades” from those who actually work with the stones and study the anomalies that are practically never brought to light from gemological aspects alone.
Manganese/Rhodonite deposits and Nephrite jade Deposits
I’ve been prospecting and California jades for quite awhile now. I’ve noticed that many Nephrite deposits have nearby Mangansese/Rhodonite deposits. This seems to be true of the Canadian deposits as well. The California deposits I can site are Trinity county River Blossom Jade Botryoidal Nephrite deposit. Mendocino county Covelo Nephrite deposit. Monterey/San Luis County Big Sur/Jade Cove Nephrite deposit, Siskiyou county Happy Camp South Fork mining Vesuvianite/Nephrite deposit. Does anyone have any additional California examples? Is there Mangansese associated with Wyoming Nephrite? Looking forward to hearing your comments.
Dear Sam,
Not being a miner I have no direct knowledge of that which you are speaking but, I do have a question or two. As I often find crystalline deposits of manganese on old stone and pottery burial artifacts I was wondering if these manganese deposits are ever found directly on the Nephrite itself, or inside the Nephrite. I have found there is a direct correlation as to the amount of manganese on an item of antiquity according to the location in which it has laid or was buried. The wetter the climate and more organics in the soil the more manganese on the item and the easier to identify under the microscope. The hardest ones to find are on the desert area burial items from colder climates that have been re-polished–these can take 45x and above to find in the tiny pits left over from where the piece has not been re-polished and once the baked on shoe polish is removed.
Have never seem manganese crystals deposited directly onto natural nephrite stones….Although I will be looking more closely from now on before cleaning any! The crystals would have a difficult time surviving the placer process by which we find “float” pieces as they are tumbled and altered by the sand and gravel abrasive motion. The insitu nephrite pieces have no indication of manganese crystals. Also the manganese deposits are not the direct neighbors of the nephrite deposits but within a couple of miles.
Hey Sam…Had a look under the microscope today at two Black Wyoming nephrite pieces I had gotten from Warren Rees and another fellow. As these pieces were only wind polished and not river tumbled I thought to take a look see and both pieces had what is commonly called out here “desert slime’ as it is organic in nature (appears much like the baked on shoe polish that has been used on reproduction stone work for years). Manganese deposits were on both pieces also, with the one of them covering large portions or the rind.
I have a couple of possibilities regarding manganese in association with Wyoming nephrite. I can’t confirm whether or not the dark dendrites sometimes present in Wyoming jade are manganese minerals or not, but they are generally assumed to be. The second is the association of Thulite (erroneously called pink jade) with Wyoming jade. Thulite is a manganese rich type of zoisite. Thulite occurs both alongside and intermingled with nephrite in Wyoming.
Peter Schilling
takingformjade.com
24toeskitty@verizon.net
68.163.170.196
Submitted on 2009/03/29 at 12:53pm
Here’s a question. Does anyone out there know what crystal structure or chemical composition causes some jades that technically test out as nephrite to have a brittle, “glassy” texture? Some of the jades I’m thinking of are the currently available Cowell black from Australia, some California black jade, and some Wyoming material including the “Game Warden” jade. At this point all I know is that when I see it I don’t like it.
admin says:
March 29, 2009 at 2:33 pm (Edit)
Hey Peter,
Not being a certified gemologist I can not site the chemical structure on the the jades that you mention here. However, under the microscope not all jades, or jadeite’s, are not created equal and that is for certain. Also, to answer your question I would believe multiple tests would have to be run on the same stone in multiple sites and in minuscule amounts. The Cowell Black, from 1972, that Donn Salt gave to me is more like the Wyoming Edwards Black, and those close to it, in that the fibrous nature of the nephrite is extremely tightly bound together with little to no chatoyancy. Yet the piece of Wyoming emerald green slab I just received from Sue Rees looks much more like the White and Black River jades of old Chinese fame. Very hard but not nearly as tightly felted as one would find in the early Cowell or the Edwards. It is my personal belief that as much as science would try to ‘pigeon hole” nephrite and jadeite, they will not be. Each bit of stone seems to have certain features common to that stone, and of course similarities exist. I think perhaps some of the problem, from the carving aspect, is more due to the types of tools used now and the types of tools used thousands of years ago. Long ago the drill speeds were not as quick and while being slower to work the stones were much less forgiving in the chipping and fracturing of different material. Like high speed polishing and slow hand polishing with the same grits should be different on different jades. Some jades after polishing look to me like old wood with the softer parts eaten away more and the harder ridges sticking up a bit. Take the famous Lake Tai Variegated nephrite for an extreme. It looks under microscopic conditions to be plates of actinolite and tremolite just jammed together and the Liangzhu, Dawenkou, and Hongshan Cultures of Neolithic China could work the material just fine. I have yet to hear much good news about California Black but have not had a chance for a look-see through my scope.
Game warden Jade is Iron rich Wyoming tremolite and should not test as jade as it is lacking the actinolite portion of true nephrite…This is also called Max Long Jade…Not a true jade