Lapidaryforum.net
Let's Rock => Rock Talk => Topic started by: Pebblehopper on February 12, 2017, 09:21:52 AM
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Does Green Grossular Garnet (aka Transvaal Jade) have a grain as real jades and serpentine have? Thanks. John
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Generally, no. The caveat is that grossular in its massive form can be intermixed with other minerals (e.g., Californite/Happy Camp which is a mix of grossular and vesuvianite) that can result in mixed hardnesses that can appear to have grain/fibrous structure.
Massive minerals (i.e., larger pieces that are formed of aggregates of micro-crystals, rather than individual visible crystals) also can appear to have grain if long crystals are oriented in certain directions. Although garnet crystals are stubby and in massive form do not tend to line up in one, grain-like direction, tiny crystals can pop out if one is too aggressive with grinding/sanding. This is not the same as the fibrous grain in some jades, however.
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Thanks R2D, It's going to be an interesting study of the differentiation between jade, serpentine, and grossular. John
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The hard , mohs 5 , Washington serpentines are not easily mistaken for jade by the experienced. The soft serps would fool no one . The dioppside mixes are the ones that fool people all the time as they mimic hard jades very well at times. Grossular comes in so many mixtures and variations that it is always suspect especially as pumpellyite can be a perfect mimic.Veins of soft jade in any of these stones is a real pain as the undercutting is awful. Fun stuff and even more fun tofind.
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Thanks Lithicbeads...I haven't done any internet searches for jade, serp, grossular knowledge yet but do you have any recommendations for books or sites that you found to be significant? Living in SW Wa. state I understand that there is this type of material in the N Cascades but have made it up there only once and that was for Listwanite (another one of my favorites). Otherwise my "finds" have been at rock shows, and club activities. Thanks. John.
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The Transvaal Jade slab I am working with is quite hard; I've cut several variable sized cabs from it and it does require a bit more patience. It has a swirly texture like those old 1970s acrylic bowling balls, which implies is underwent some mixing/flow during its formation/cooling.
Just a data point to consider in your review of responses.
David.
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Grossular and vesuvianite are usually as hard as quartz. They are probably always mixed in Washington with a bit of pumpellyite which is the same hardness. I know of no resources. Us old collectors learned together in the field and in the UW and Western Washington University libraries. Our developed instincts were pretty much confirmed by a scientist who tested many of our pieces with x-ray diffraction technology. Buying grossular etc from Poobas on ebay is an inexpensive and easy way to get very nice rough. He listened well to more knowledgeable folks when he started and he is a very honorable seller. I have bought thousands of dollars of rough from him and I have absolutely no complaints.The rocks will be a bit darker than pictured is the only thing to remember. He tests and tlls the hardnesses on his cut rough. Want no undercutting go to the diopside mixes. You can often get wonderful botryoidal jade stones from his diopside mixes, the best deal on ebay .
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David, thanks for your comment...now I excited to get started on that Transvaal.
Lithicbeads, what a wealth in your suggestion...I'm on it! Would you confirm the sellers name on ebay. I'm not finding anything under that even in advanced search. Thanks
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http://www.ebay.com/sch/poobasjade/m.html?ssPageName=STRK%3AMEFSXS%3AMESOI&_trksid=p2053788.m1543.l2654
:icon_sunny:
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Sorry. He had a very nice inexpensive grossular on buy it now so buy it I did.
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Hummingbirdstones: Thanks for the direction...got it now.
Lithicbeads: Wow, Poobas is quite the Jade "honeyhole".
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Dear Hummingbird: Thanks for the poobasjade tip; nice page with some tantalizing items.
:blob1:
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You're welcome! :icon_sunny:
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Remember that almost all Washington jades are very hard to sand and polish with the diopside mixes being the exception. The grossulars are usually fine.
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Thanks lithicbeads, does that include the "Washington Blue Jade" and cats eye too?
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Cats eye jades do not change in my experience but they can be unpolishable due to obscenely bad undercutting. They are most likely full of asbestos so be forewarned. The blues normally go bye bye in a few months. Cutting makes no difference as it is simply oxidation due to exposure to air.Blues cut with oil will ofetn oxidize to off blue or light brown within seconds. I can recut many of his nodules that look like they have a haze over the surface from oiloxidation. If I use water the stone will come from the saw much brighter but will oxidize within a few weeks. Mohs 6 is a clue that the rock may have a high diopside content and be stable.Tricky game jade is for all players at all levels.
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Thanks Lithicbeads, "tricky game..." LOL...I was going to say 'let the games begin' but the game has already begun. Thanks for the thoughts on the cat's eye and blues. At this stage in the game I think I'll be sticking with the BC's that I already have in the studio and not plunge into the others.