They are some of the most common ones in the group of silicate minerals.
Amphibole minerals include hornblende, glaucophane, riebeckite,
termolite and anthophyllite.
is a dark,
mafic mineral rich in iron and/or magnesium. It can form
prismatic crystals, or occur in massive, granular, fibrous, bladed,
columnar or compact habit. It is dark green, brown or black in colour.
It is found in rocks like amphibolites, trachytes, diorites,
granodiorites and schists.
Glaucophane. By Tjflex2 via Flickr.com
is also a mafic
mineral, which means that it contains large amounts of iron and
magnesium. It is a blue, grey or bluish black mineral that can for
prismatic or acicular crystals or be granular, fibrous or massive. It
is found in metamorphic
that form in low temperatures and high
pressures such as blueschists, greenschists and eclogites.
Riebeckite. By Kotomi_via
is a dark mineral
that can have long prismatic crystals like on the photo here; or it can
be fibrous or massive. It is dark blue, black or greyish blue in
colour. It is transculent and it can also occur as asbestos, which is
when it is called crocidolite. It forms in many different igneous
such as syenites, alkaline granites, and rhyolites as well as
metamorphics such as schists.
Hadley Paul Garland via Flickr.com
can occur in long
bladed crystals, or it can be granular, massive, fibrous, columnar or
plumose. Crystals are often twinned. It can be white, brown, violet,
pink, grey, green or colourless. It can also form asbestos. When fine
grained and massive, it is called nephrite jade. It forms in
serpentinites, dolomite limestones and in low grade schists.
Anthophyllite. By Asbestorama via Flickr.com
massive, lamellar, fibrous or occur as asbestos. Less often it forms
prismatic crystals which can be twinned. It can be grey, yellowish
brown, purplish brown, greenish brown, green or black. It is found in
granulites, metaquartzites, gneisses,
schists, amphibolites and