Hematite: the Other Red Metal.
Hematite is Iron
Oxide. It forms hexagonal crystals and is most often red-black or
metallic, even in nature. The streak is red. This is why we do a
streak test-- samples are often metallic but the streak is red to red-brown.
Often when pyrite
psuedomorphs (rusts) it is changing to hematite. It was thought for
decades this was the case with the Pyrite psuedomorphs from Pelican Point
in Utah County . But, with recent research,
it was determined they changed to Goethite. Goethite is a polymorph of
hematite, meaning that they are the same mineral with different chemical
characteristics.
All the red sandstone
in Utah (and
the rest of the west) is caused by iron in the sand. There is enough iron
that it rusted causing the red. This is the environment that caused
the “Moqui Marbles” to form. They are only bubbles of hematite that
formed under the sandstone by ground water.
At a lot of the old
copper/silver/lead mines in the western part of the state you find red
dirt. It is very crumbly and makes collectors very dirty when they dig in
it. This is usually limonitic gossan. Gossan is hematite in
limestone that was baked by super heated ground water when the ore deposit was
being formed.
Most of the red in the
agate & jasper & petrified wood in the West is caused iron staining them
that color.
Not all the red in all
these cases are caused by hematite. However, most is related in one way
or another.
The hematite beads
that are so popular are not really hematite. They melt hematite down and
pour it into molds to make all those beads. This is why they are so
cheap. If someone was cutting and polishing all those shapes they would
be very expensive.
Thanks for this interesting post. I'm certainly a novice when it comes to geology but I did enjoy reading this.
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Wow, what a cool theme!
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