Hematite

Authors: Glory Schulze and Nick Ribali

Mineral Name: Hematite

Chemical Composition: Fe2O3 - Ferric Iron oxide

Color: Hematite can vary in color from black to silver grey, or rusty red to brown.

Streak: The streak left by hematite is a red to reddish-brown color.

Hardness: 5-6.5

Cleavage/Fracture: Hematite has uneven fracture. Uneven fracture is when the breakage of a mineral is left with rough and/or irregular surfaces. (5)

Crystal Form: The crystals form is trigonal. This means the crystals have threefold symmetry with four axes, three of those axes are the same in length, and these 3 axes are at an angle of 120° from each other. The forth axes can be shorter or longer but it has to lie at a right angle toward the other corners. (5)

Luster: Earthy, dull, can be metallic.

Special Features: Hematite can be identified by its paramagnetism. Paramagnetism means that the ore is slightly attracted to magnetic fields. Hematite is magnetic due to its high concentration of iron. (5)

Varieties: Hematite can show up in many forms. Hematite can be identified as Kidney Ore hematite, which looks like a kidney. Oolitic hematite can be identified by its very small round spheres that are pressed together in a fashion similar to sedimentary rocks. Specular hematite has a metallic luster and contains mica flakes. (4)

Mineral Group: Hematite falls in the oxides mineral group, and specifically subdivided into the group simple oxides. Minerals in the oxide group are made of one or more metallic elements in combination with oxygen, water, or hydroxyl. Simple oxides are classified as the minerals made of metallic elements specifically combined with oxygen. (5) The composition of pure hematite is about 30% oxygen and 70% iron (4).

Environment: Hematite can be formed in many geologic situations. The most important deposits of hematite formed in Earth’s early oceans. Oxygen combined with dissolved iron in these oceans and created what are called banded iron formations in Earth’s history. (4) Hematite can also be formed during magmatic differentiation, during hydrothermal precipitation events, and in contact metamorphism events.

Associated Rock types: Hematite can be found in igneous, metamorphic and sedimentary rocks, like . Hematite is very commonly found in banded iron formations, like taconite (4). Banded iron formations are sedimentary rocks that contain layers of hematite and other minerals like quartz, goethite, and pyrite, among other (6). Rocks that contain magnetite, like basalt, can be weathered and eventually contain hematite.

Occurrence in North America: Hematite is mainly found in mines around the western Area of Lake Superior. Large deposits of hematite have also been discovered in the state of Utah, and in numerous locations in Arizona such as Aztek Peak. (5)

Economic Uses: Hematite is very popular in the mining community for its iron-rich composition. When the iron is extracted it can be used for making tools, iron bars, and steel beams. Hematite can also be ground down into a fine powder. In early human societies that had access to this mineral used the powder as paints and dyes. (3)

Industrial Uses: Similar to the economic uses of hematite, it is widely used for the production of iron and steel. Over 90% of North America’s iron is from hematite (3).

First Notable Identification: Hematite was named by Theophrastus around 300-325 BCE. Theophrastus gave it the greek name “aematits lithos” meaning “blood stone”. In 79 AD this was translated by Pliny the Elder to “haematites’’ meaning “bloodlike”. (2) Hematite was found to be a useful material for cave paintings over 40,000 years ago (4).

How We Identified It: We identified hematite by the mineral’s color, hardness, streak and luster. The minerals we took pictures of had a lot of red in them and were very dull in their luster. A few of our examples were a steel grey color and had a metallic shine to them. The streak of hematite left behind is a red-rust color.

Don’t Confuse It With: Hematite is very commonly confused with magnetite but can be confused for galena as well. Hematite and magnetite are very close to the same mineral because they are both iron oxides and therefore very easily confused. Black colored samples of hematite are often confused for magnetite. However, hematite has a red streak while magnetite has a black streak. (1) Galena has more noticeable differences from hematite but can still mistaken for it as it’s luster is also metallic. A few main ways to tell these two apart are their hardest, streak and cleavage. Galena is far softer at 2.5 and leaves a lead grey streak, whereas, hematite has a measured hardness of 5-6.5 and has a red streak. If all else fails hematite has uneven fracture while galena has cleavage and its breakage forms cubes, this means it has cleavage in three directions. (3)

Bibliography:

1. Goeke, Elli “Mineralogy: magnetite & hematite – minerals of the week #2” Life in Plane Light. N.p., n.d. Web. 12 Feb. 2018. https://lifeinplanelight.wordpress.com/2011/02/28/mineralogy-magnetite-hematite-minerals-of-the-week-2/.

2.“Hematite.” Hematite: Hematite Mineral Information and Data. N.p., n.d. Web. 12 Feb. 2018. www.mindat.org/min-1856.html.

3.“Hematite.” University of Montana. N.p., n.d. Web. 12 Feb. 2018. www.esci.umn.edu/courses/1001/minerals/hematite.shtml.

4. King, Hobart M. "Hematite." Geology. N.p., n.d. Web. 12 Feb. 2018. https://geology.com/minerals/hematite.shtml.

5.“Minerals.net.” Hematite: The Mineral Hematite Information and Pictures. N.p., n.d. 28 Feb. 2011. Web. 12 Feb. 2018. www.minerals.net/mineral/hematite.aspx.

6.“The Mineral Hematite” Amethyst Galleries Mineral Gallery. N.p., n.d. Web. 12 Feb. 2018. http://www.galleries.com/Hematite.