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.
Hardness is 2.5, streak lead gray, and specific gravity 7.4-7.6. Galena is a widespread mineral deposited by hydrothermal solutions as large, irregular masses in dolomitized limestones and in zones of contact metamorphism and as veins in volcanic rocks. It often contains enough silver to be mined as a silver ore.