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Calcite

MNHN N°194.11

visu_8 infos

FROM : Rio Grande do Sul, Brazil
SIZE : 23 x 19 cm

general description

This specimen is made of a chalcedony base in which lays 3 prismatic crystals entwined. The bigger crystal measures 18 cm and 5 cm in diameter.

These crystals show 3 steps of their history: in the middle, there is a well-formed crystal, colorless and gemmeous. A milky white translucent calcite embraces this crystal. The third step is an empty space between the crystal and the calcite coming from a dissolution.

This sample was formed in the basalt of Rio Grande do Sul, Brazil. Acquired thanks to support from Total, it is currently exposed in the Treasure Room, within the Gallery of Mineralogy of the Museum national d’Histoire naturelle

Photography 3D view: Louis-Dominique Bayle, © MNHN.

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The Species page

Identity card

SPECIE : Calcite

HISTORY : Name inspired from the Latin word "calx" meaning burned chalk

Species first described in 1836 by Johann Karl Freiesleben (1774-1846), officer of the mines of Saxony

Type-locality: undefined because species already known from the Ancients
ANCIENT NAME : Spath d'Islande, chaux carbonatée

CHEMICAL FORMULA : Ca CO3
CRYSTAL SYSTEM : Rhomboedric
COLOR : Colorless, white, color depending on inclusions
DIAPHANIETY : Transparent to opaque
LUSTER : Vitreous, pearly
STREAK : White
MORPHOLOGY : Well-formed crystals common, forming concretions
HARDNESS : 3,0
DENSITY : 2,71

CHEMICAL CLASS : V - Carbonates, nitrates
GROUP : Calcite
STRUNZ CLASS BEFORE 2001 : 5/B.02-20
STRUNZ CLASS AFTER 2001 : 5.AB.05

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