Hornblende is actually the name given to a series of
minerals that are rather difficult to distinguish by
ordinary means. The iron, magnesium and aluminum ions
can freely substitute for each other and form what have
been distinguished as seperate minerals. The minerals
are given the names Magnesio-hornblende, Ferrohornblende,
Alumino-ferro-hornblende and Alumino-magnesio-hornblende.
These minerals are obviously named for their chemistries
although there is little to distinguish them in the
field. The iron rich members of the series are more
darker black and less likely to be translucent.
Hornblende is not often a collection mineral because
good crystals are somewhat difficult to find even though
the mineral is widespread. It is almost always opaque
and black and not very attractive. However a few specimens
are extraordinary and make for valuable specimens. Some
crystals can grow to a fairly large size of several
feet long and nearly a foot across. Other specimens
of hornblende can be acicular clusters or needle thin
crystal aggregates. Many times a specimen of a more
valuable mineral will be accented by the opaque black
crystals of hornblende.