Azcárate Quarry (Azkarate Quarry), Eugui, Esteríbar, Navarre, Spain

MgCO₃

Crystal System: trigonal
Colour: colourless, white, greyish-white, yellowish, brown, faintly pink, lilac-rose.
Lustre: vitreous
Habitus: rombohedral or more rarely prismatic or scalenohedral crystals. Also in massive porcellanaceous aggregates, coarse to fine grained.
Hardness: 3½ - 4½
Fracture: conchoidal
Cleavage: perfect on {10-11}
Density: 3.01 g/cm³ 
Origin and geological occurrence: it is a common alteration mineral of ultramafic rocks as peridotite or serpentinite deriving from circulation of CO₂-bearing H₂O. It occurs in pegmatite rocks and hydrothermal veins.

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Smorf link

Samples:

5.14 Magnesite Porcellanaceous massive fine-grained aggregate. #carbonates, economic minerals