Science Fair Project Encyclopedia
Emery (mineral)
Emery (also known as iron spinel and hercynite) is a common impure variety of the mineral corundum.
It is black or dark gray in colour, less dense than translucent-brown corundum with a specific gravity of between 3.5 and 3.8 and does not form any regular large-scale crystalline structures. It has a Mohs hardness of 8.
In addition to aluminium oxide, emery contains an iron-bearing mineral such as magnetite or hematite and trace impurities such as magnesia, mullite , titania or silica.
Crushed or naturally eroded emery (known as black sand) is used as an abrasive.
Last updated: 06-01-2005 23:35:22
12-19-2008 14:25:18
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details