Another Example - Mineral 1

Distinguishing Physical Properties:

• Color: notice that this is a very dark-colored mineral (usually varieties are black, or possibly very dark green)

• Hardness: this mineral is relatively hard and can scratch glass (5-6 on Moh's scale)

• Cleavage - Is not as pronounced as the first sample - with a magnifying glass or hand lens you might be able to find cleavage planes at every 60 and/or 120 degrees

• Note: Unfortunately, this mineral is very easily confused with pyroxene minerals that exhibit the same hardness and dark coloration. It is distinguished from pyroxenes by cleavage angles - pyroxene mineral surfaces/cleavage planes are almost 90 degrees (square shape). And different varieties of this mineral are so similar in appearance that often they can only be distinguished from one another by examination under an optical microscope. This mineral is an important component of many intermediate igneous and metamorphic rocks.