Mineral description : Humite

Humite (or clinohumite) as a thin vein in calcite, from Ihalainen, Finland.

Mineral class	Silicates : Nesosilicates : Olivine group.
Chemical formula	Mg7(OH,F)2(SiO4)2
Crystal system	Orthorombic.
Habitus	As rounded grains or tabular crystals. Also as grains or aggregates partly transformed into serpentine.
Cleavage	[001] poor.
Hardness	6-6.5
Density	3.1-3.2
Color	White to light yellow, yellowish green when transformed into serpentine. Also brown and orange.
Streak	White.
Luster	Vitreous, transparent to translucent.
Description	Humite is the naming member of a group of minerals called the humite group. The crystal structure of the humite group minerals is as layers of silicate and oxide. The silicate layer have the same structure as olivine and the oxide layer resembles brucite. In the case of humite it consists of three olivine layers between each brucite layer.
Occurance	In hydrothermal veins and contact or region metamotphosed dolomitic rocks.
Associates
Notes	Very easy to mistake for chondrodite. Type locality : Mount Somma, Vesuvius, Italy. Named after Sir Abraham Hume.
Locations	A relatively rare mineral in Sweden. Ladugruvan, Persberg, Värmland. As up to 1 cm yellow grains and crystals, or yellowish green grains and aggregates strongly transformed into serpentine. Note : Tallgruvan doesn't exist any longer. It's been incorporated in Gåsgruvan as the latter have grown in size.

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