Laacher See Volcanic Complex, Germany

KMg₃Si₄O₁₀(OH)₂

Crystal System: monoclinic
Colour: brown, gray, green, yellow, or reddish brown
Lustre: vitreous, pearly
Habitus: pseudo-hexagonal tabular to prismatic crystals. Also as coarse-grained, platy aggregates, and as small scales
Hardness: 2 - 3
Cleavage: perfect {0001}
Density:  2.79 g/cm³ 
Origin and geological occurrence: it occurs in ultramafic rocks (kimberlite, peridotite, lamproite, serpentinite) and in metamorphosed dolostone and Mg-rich limmestone

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Smorf link

Samples:

9E.9 Phlogopite Micaceous crystals with calcite #phyllosilicates