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Porphyry
Porphyry is a general term that is used rather loosely for igneous rocks which contain relatively large isolated crystals set in a fine-grained groundmass.
The porphyry pictured here has pinkish coloured clinozoisite crystals set in a ground mass of dolerite.
Click here to view cut & polished specimens of porphyry for sale
We mine a second variety called "Chinese Writing Stone" . It is a porphyritic basalt with groups and rosettes of plagioclase feldspar. Age of the Mt. Roe baslt that it occurs in is approx. 2,800 million year. The location is in the Pilbara region of Western Australia near Whim Creek.
Another variety occurs in farming country near the town of Beverley not far from Perth. Someone once said that the feldspar crystals in the dolerite looked like cat foot prints. Now the name "cats paw" porphyry has stuck.
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