Crystal Description:
Orthorhombic
The crystals have the basic forms that are characteristic of
pyrite, namely, simple cubes. There are a number of other forms
that also can be found from time to time the most common being
the pyritohedron. On some occasions they form “iron
cross” twins. The crystals tend to form in interpenetrating
clusters rather than single crystals. The individual cubes range
in size from .5” (12mm) up to 4” (10cm), and the
clusters range up to 15” (38cm) in major diameter. In some
areas, “stringers” of crystals have measured up to
36” (1 meter) in length.
Physical Properties:
Color - Dark brown to almost black
sometimes orange stained from Fe oxides
Hardness - 5 - 7
Luster - Adamantine-metallic
Specific Gravity - 3.3 - 4.3 (depending on pyrite content)
The crystals generally form in clusters rather
than in individual crystals. The crystals vary greatly in the
degree of replacement, ranging from almost 100% Goethite to
nearly 99.9% pyrite at the other end; most are at least 60% +
pyrite. In some layers, the crystals form in simple clusters made
up of 2 - 5 crystals, while in other layers the individual groups
can be made up of hundreds of crystals. The crystals are very
sharp showing almost degradation.
