known as Apache tears, is a volcanic glass which is
generally black, but is occasionally red, brown, gray, green
(the rarest variety), dark with "snowflakes," or even very
clear. It is said, probably to be the most challenging stone
in crystal work. It is in fact a volcanic glass and has been
used in past by many native cultures to make knives.
Obsidian has several varieties. It contain tiny bubbles of
air that are aligned along the layers created in the process
of molten rock flowing just before being cooled. These
captured bubbles produces interesting effects like golden
sheen or a rainbow sheen. These types of stones are named as
Sheen Obsidian and Rainbow Obsidian respectively. There is
also Snowflake Obsidian, which has small, white and radially
clustered crystals of cristobalite in the black glass and it
produces a blotchy or snowflake pattern in it.
The stone is often confused with smoky quartz due the
similar properties and also because of similar chemistry. It
is found in Italy, Mexico, Scotland, Arizona, Colorado,
Texas, Utah and Idaho. The specific gravity is 2.6 and
hardness 5 - 5.5 on Mohs scale.