In the United States, anthracite is mined mostly in eastern Pennsylvania. This mineral is named after the French physicist Biot, who lived from 1774 to 1862. Large sheets of biotite were once used as heat-resistant windows on ovens and furnaces. These are very closely related. Calcite is a very common mineral.
Clear calcite is used in special kinds of microscopes.
Feldspars are the most common of all minerals. Certain kinds are used in glass making, while others are set in jewelry. This is the word the Greeks used for a kind of lead ore. To the Romans, galena was what was left after the lead was melted out of the ore. Galena is the ore from which we get most of our lead.