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| Raised crystals /Relic crystals |
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Posted By: Mike Allen Posted Date: Feb 04, 2009 (12:39 AM) |
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Message Dear Sirs, I note with interest the discussion between Mirceau Veleanu and Wingchuntaiji about raised crystals.I have seen similar discussions in other forums. If possible I would like to kill this myth about raised crystals. It is said that raised mineral crystals are caused by clay minerals or similar forming in and around large crystals in a rock matrix. The clay minerals as they form occupy a larger volume than the original mineral so exert a force to push out the larger crystal.This phenomenon does occur in nature, but the surface of the rock will have a distinct appearance. Yes, there will be raised crystals, but also there will be pits in the shape of the large crystals that have fallen out. There may also be signs of breakage on the surface as the crystal has been forced up and out it has broken the surface. I have have never seen anything like this on jade items. I have seen what appear to be raised crystals but with out the pock marks of the missing ejected crystals. These are relic crystals that remain after the surface has been corroded away by some agency. What has happened here is the finer matrix being more susceptible to corrosion, has dissolved away, leaving the larger crystal behind, so relative to the surrounding fine matrix the crystal appears raised. Now, literally the $64,000 question is what caused the relic crystal? Natural agencies such as soil acids, decomposing body fluids may cause corrosion. Unfortunately, these actions can be imitated by modern chemical treatments. One clue to age and natural processes being responsible is that there can be a defined zoning in the article, due to the migration of ions such as Fe, which causes banding/zoning. This is very difficult to imitate. However, this zoning may not always occur, and as usual one must look at the holistic nature of the jade piece, design, tool marks etc, before reaching the final verdict. Mike Post a Response |
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