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Formula: ☐Ca2(Fe2+4Al)(Si7Al)O22(OH)2
Inosilicate (chain silicate), amphibole,
hornblende root name group,
calcium amphibole subgroup,
amphibole supergroup, forms a series with
magnesio-hornblende
Crystal System: Monoclinic
Specific gravity: 3.12 to 3.30 measured
Hardness: 5 to 6
Streak: Pale grey-green, grey-white
Colour: Dark green to black, greenish-brown, more rarely lighter green
Solubility:
Common impurities: Ti,Mn,Na,K
Environments
Plutonic igneous environments
Pegmatites
Metamorphic environments
Ferro-hornblende is found in granite and
granodiorite, and is common in
amphibolite and schist
(Webmin, HOM). Associated minerals include hedenbergite
(in granite), biotite,
epidote, albite and
quartz (in amphibolite)
(HOM).
Localities
At the Fraser Mine, Levack Township, Greater Sudbury, Ontario, Canada, the
amphibole that overgrows many of the
actinolite and
magnesio-hornblende cores falls into one of two categories:
(a) iron-rich, halogen-poor amphibole,
ranging in composition from ferro-actinolite to
ferro-hornblende
(b) iron-rich, chlorine-rich amphibole
ranging in composition from hastingsite to
potassic-chloro-hastingsite
(CM 37.1385-1403).
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