chu snying
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ཆུ་སྙིང
precious stone, salt [JV]
salt [IW]
(sman) Agate (dGa' ba'i rDo rje 2018)
chu snying me yi 'jigs pa srung skyob nus / zhes pa ni / dkar la sngo ba shel lta bu chu nang du bcug na dangs pas mi mthong bar chu dang 'dra zhing / me steng du bzhag na me 'chi ba dbyibs tsha tsha 'dra ba gla ba'i ril ma tsam 'byung bas rdog po res gser srang re ri ba'o // (Shel gong shel phreng, pdf p 083.3)
Illustrations : dGa' ba'i rDo rje 2018 (n°018) Agates
The Shel gong describes it as white with a blue tint, of crystal-like appearance.
In the medicinal gemstone section is a second notice for chu yi snying po, a different gemstone.
Agates are part of the group of microcrystalline quartz or chalcedony. They are mostly found as nodules in cavities, the latter were formed when gas bubbles were trapped in cooling lava. These were filled with hot, silica-rich water which crystallised in a complex process into agates. When silica concentration in the silica gel is low, quartz crystals form around the center which remains hollow. That might well be the chu snying type. Occasionally they can be coloured, like amethyst or smoky quartz.
Higher silica concentrations form agates which are composed of bands of chalcedony fibres, and because the colors and patterns found in agates are so varied and so characteristic for the respective localities, that there is a confusingly large number of ever-changing varietal and trade names (mindat.org). A number of tibetan terms denotes forms of chalcedony, some in the gem section, some in the stone section : mchong (agate), rdo'i snying po (agate), chu snying (agate), bel snabs (chalcedony), khra man / dkar khra men, khyung skyug (jasper) or gzi (onyx, sardonyx).
Johannes Schmidt (talk) 14:16, 29 February 2024 (EST)