sparry magnesite - pinolith - display specimen of a very unusual metamorphic rock from Austria
Pinolith is an unusual metamorphic rock, sometimes called pinolite, and is a form of sparry magnesite, The gray matrix is a graphite pigmented dolomitic limestone. The white pine-nut-shaped crystals are magnesite - magnesium carbonate, MgCO3.
Near Sunk, Hohentauern, Austria, millions of tons of magnesite have been mined in the 1800s and 1900s for the magnesium content. The magnesite is calcined or burned with charcoal at temperatures above 900˚C to form magnesium oxide used in the chemical industry and in the heat resistant refractory bricks used in steel making to protect furnace walls and ladles from hot liquid steel.
Small pinolith bodies that are associated with the magnesite were discovered in 1873 and still produce specimens, usually as a semi-precious stone or decorative rock.
In the eastern Alps, during the Late Triassic according to one model, buried marine evaporitic brines, rich in magnesium, were mobilized either by magmatic or metamorphic processes in the underlying crystalline rocks or by the compaction of Triassic platform carbonates, leading to the formation of lens-shaped orebodies of magnesite, a relatively uncommon carbonate.
These slabs are cut but not polished. Both sides of each are shown.
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