What is a variable speed drive? A variable speed drive is a piece of equipment that regulates the speed and rotational force, or torque output, of an electric motor. The background and technology. There are millions of motors in use in industry and offices around the world.
The specific gravity for Obsidian is 2.35, it's refractive index is 1.48-1.51, and it's double refraction is None. History Obsidian is named after a Roman, Obsius.
Ferromagnesian silicates are those minerals containing ions of iron (iron=ferro) and/or magnesium in their structure. Because of there iron content, ferromagnesian silicates aâ¦re dark in color and have a greater specific gravity, between 3.2 and 3.6, than nonferromagnesian silicates. The most common dark silicate minerals are olivine, the pyroxenes, the amphibloes, drk mica (biotite), and garnet. 7 people found this useful.