last modified: Tuesday, 26-May-2009 03:45:50 CEST
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Plasma is a more or less evenly leek-green, slightly translucent to opaque chalcedony. Sometimes plasma is considered the green variant of jasper, and hence is supposed to be opaque. There is no strict taxonomy, however, so any green chalcedony that is not chrysoprase may be called plasma. Green translucent chalcedony used to be called prase, and some people still call it so, but today the meaning of the word has changed and refers to green macrocrystalline quartz.
Specific PropertiesThe color can be a bright to dark leek-green, and is caused by different embedded materials, typically chlorite or actinolite. I am not sure if chalcedony that is green due to other embedded minerals can be called plasma (except nickel-compounds, as that would be a chrysoprase).
OccurrencePlasma forms nodules and amygdules in volcanic rocks. It can also be found as vein fillings.
Locations and SpecimenPlasma of good quality comes from the Deccan Traps in India.
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