Thursday, 14 February 2008

Mineral Spot: Thomsonite...

Thomsonite and natrolite are two relatively common zeolite minerals that occur in cavities in basalt. They are often prismatic and colourless, and occur together, but they are easy to tell apart, particularly under magnification. The thomsonite occurs as thin bladed crystals with flat terminations, whereas the natrolite crystals have a square cross-section and pyramidal terminations. This photo is of thomsonite in the foreground, with the reflective face being one side of a natrolite crystal, and is about 4mm across. The specimen comes from Cairns Bay, Flinders, Victoria.

It is also a specimen that will be included in one of my auction lots this week at OZtion...

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