Actinolite is an amphibole
silicate mineral with the chemical
The name actinolite is derived from the
Greek word aktis (ἀκτίς), meaning "beam"
or "ray", because of the mineral's
fibrous nature. (This word is also the
origin of the name of the chemical
Actinolite is an intermediate member in
a solid-solution series between
and iron-rich ferro-actinolite,
and Fe ions can be freely exchanged in
the crystal structure. Like tremolite,
asbestiform actinolite is regulated as
Actinolite is commonly found in
metamorphic rocks, such as contact
aureoles surrounding cooled intrusive
igneous rocks. It also occurs as a
product of metamorphism of
The old mineral name uralite is at times
applied to an alteration product of
primary pyroxene by a mixture composed
largely of actinolite. The metamorphosed
gabbro or diabase rock bodies, referred
to as epidiorite, contain a considerable
amount of this uralitic alteration.
Fibrous actinolite is one of the six
recognised types of asbestos, the fibres
being so small that they can enter the
lungs and damage the alveoli. Actinolite
asbestos was once mined along Jones
Creek at Gundagai, Australia.
Some forms of actinolite are used as
gemstones. One is nephrite, one of the
two types of jade (the other being
jadeite, a variety of pyroxene).
Another gem variety is the chatoyant
form known as cat's-eye actinolite. This
stone is translucent to opaque, and
green to yellowish green color. This
variety has had the misnomer jade
cat's-eye. Transparent actinolite is
rare and is faceted for gem collectors.
Major sources for these forms of
actinolite are Taiwan and Canada. Other
sources are Madagascar, Tanzania, and
the United States.