Monday, April 09, 2012
H is for Hematite
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
. 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. Utah County
All the red sandstone in
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. Utah
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.