Description:
Pyrite is the classic "Fool's Gold". There
are other shiny brassy yellow minerals, but pyrite is
by far the most common and the most often mistaken for
gold. Whether it is the golden look or something else,
pyrite is a favorite among rock collectors. It can have
a beautiful luster and interesting crystals. It is so
common in the earth's crust that it is found in almost
every possible environment, hence it has a vast number
of forms and varieties.
Bravoite is the name given to a nickel-rich iron sulfide.
It is closely related to pyrite but contains up to 20%
nickel. Some mineral books treat it as a variety of
pyrite. Pyrite is a polymorph of marcasite, which means
that it has the same chemistry, FeS2, as marcasite;
but a different structure and therefore different symmetry
and crystal shapes. Pyrite is difficult to distinguish
from marcasite when a lack of clear indicators exists.
Pyrite's structure is analogous to galena's structure
with a formula of PbS. Galena though has a higher symmetry.
The difference between the two structures is that the
single sulfur of galena is replaced by a pair of sulfurs
in pyrite. The sulfur pair are covalently bonded together
in essentially an elemental bond. This pair disrupts
the four fold symmetry that a single atom of sulfur
would have preserved and thus gives pyrite a lower symmetry
than galena. Although pyrite is common and contains
a high percentage of iron, it has never been used as
a significant source of iron. Iron oxides such as hematite
and magnetite, are the primary iron ores. Pyrite is
not as ecomonical as these ores possibly due to their
tendency to form larger concentrations of more easily
mined material. Pyrite would be a potential source of
iron if these ores should become scarce. Pyrite has
been mined for its sulfur content though. During WWII,
sulfur was in demand as a strategic chemical and North
American native sulfur mines were drying up. A sulfide
deposit near Ducktown Tenn. was found to be able to
mine pyrite and other sulfides such as pyrrhotite and
pentlandite and produce the needed sulfur as well as
iron and other metals. The sulfur was used in the production
of sulfuric acid, an important chemical for industrial
purposes. Now most sulfur production comes from H2S
gas recovered from natural gas wells. |
