Tamarugite is a rare sodium aluminium sulphate with the formula NaAl(SO₄)₂·6H₂O, which usually appears as white crusts made up of tiny crystals. In this specimen it is accompanied by kröhnkite, another sodium sulphate but this one with copper Na₂Cu(SO₄)₂·2H₂O, in the form of blue-green, translucent elongated crystals. Both rare species!
NOTE: These specimens are natural, formed in a mine, and have nothing to do with those from mine water rafts that were sold years ago at exorbitant prices.

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