The amount of light able to be passed through a mineral determines its transparency.
Light is able to pass through transparent minerals; translucent minerals partially let light pass
through; and opaque minerals do not let any light through. A mineral type can exhibit more
than one level of transparency, and, in fact, most transparent minerals also occur in
translucent forms. Flaws, inclusions, and impurities degrade the transparency of a
mineral. Many minerals exhibit some forms that are completely transparent and other forms
that are completely opaque. Such minerals are labeled in the transparency section of this
guide as transparent to opaque. A number of minerals may seem opaque, but when held to a
light source seem to be letting a small amount of light pass through at its corners. A
specimen with such characteristics is said to be transparent in thin splinters or
sections. All minerals with a metallic luster are opaque. Most minerals
with a submetallic luster are
translucent in thin splinters.
How to use transparency as an
Transparency isn't normally used as an identification mark. It can, however, eliminate some mineral
possibilities when trying to identify a mineral. Some minerals that are normally
transparent may be clouded by inclusions
and appear partially or fully opaque. In such cases, one can view the mineral through
light and see if any light passes through.
How to test using transparency
Transparent minerals are visible to the eye. Do distinguish between translucent
and opaque minerals, one should view the mineral in a strong light source to see
if light can be passed through at all. A distinction can be
noticed between translucent, translucent in thin splinters, and opaque minerals.