Stone of the Week - Hematite

Monday, February 11, 2008
The name Hematite comes from the Greek word haima, meaning blood, probably due to the red streak color Hematite has. Hematite is an iron oxide, and is found in all three rock types. It can form in a variety of manners, including hydrothermally, as concretions, or even filling voids in rock. One of the most famous geologic formations in the world is the banded ironstone, which has alternating bands of shale or chert, with hematite or magnetite. Hematite has even been found on Mars, known as the famous Martian ‘blueberries’!

One of the most famous and most photographed geologic sites in the world is the banded ironstone formation.


Hematite is commonly seen as a gray mineral, however it can also form as a brown, brownish red, bright red, or shiny black color. It can form as tabular or rhombohedral crystals, sometimes forming a rose shaped mass called an iron rose, which is highly collectible. Other habits include massive, crusty, granular, radiating fibrous, and reniform or botryoidal. Specular hematite or Specularite has aggregates of silvery, metallic, flakes or tabular, anhedral crystals.

Specular hematite or specularite as photographed from two different angles.


Hematite has several uses, one of the most common being as an ore of iron. It has also been used in polishing powders, and included in red paint since ancient times. The Aztecs used the specular hematite as mirrors by grinding it up and creating polished flat pieces. Hematite is also found in jewelry, though most of the beads available are manmade/synthetic hematite.

Most hematite used in jewelry is actually synthetic, often called Hemalyke.


If you have a stone you would like to know about, please feel free to leave a request in the comments section. Have a mystery stone? Leave a link in the comments to a picture of it, and it may be featured as a part of this series!


Hematite Facts:
Chemical composition: Fe2O3
Color: Brown, Brownish Red, Red, Gray, Black
Habit: Crystals, massive, granular, earthy, fibrous, reniform or botryoidal
Fracture: Conchoidal
Cleavage: None
Luster: Dull, Metallic
Hardness: 6.5 (crystalline)
Specific Gravity: 5.3
Streak: Red, Brownish Red
Occurrence: Worldwide, abundant in the Lake Superior region


References
A Guide to Rocks and Fossils by B. Busbey III, R. R. Coenraads, P. Willis, and D. Roots. Published 2002 by Fog City Press. ISBN: 1877019518

Rocks, Minerals, & Fossils of the World by C. Pellant and R. Phillips. Published 1990 by Little, Brown and Co. ISBN: 0316697966

Mindat – Specularite. http://www.mindat.org/min-5574.html

Wikipedia – Hematite. http://en.wikipedia.org/wiki/Hematite

3 comments:

MargeInReno said...

Wow!! That's a super article about Hematite. I didn't know a lot of that info ... and I love hematite. Great blog. ~Marge~

TallGiraffe said...

The picture of the banded ironstone is awesome. It looks like it has a wood grain. I'd love to see it in person.

Bijoutery said...

It was really cool - that particular site was at a mine, and according to my geol. prof. photos of it are in more books than any other site in the world! The hematite was the really sparkly kind too - very pretty with the bright red!