ROCK+LOGIC

=// Rocks and Minerals Reference Sheet //= ANTHRACITEThis comes from the Greek word "anthrax", meaning "coal." Anthracite is commonly referred to as "hard coal." In the United States, anthracite is mined mostly in eastern Pennsylvania. BIOTITEThis mineral is named after the French physicist Biot, who lived from 1774 to 1862. It is a kind of mica, often called "black mica." Large sheets of biotite were once used as heat-resistant windows on ovens and furnaces. CALCITE and CHALKThese are very closely related. Both names come from the Latin word "calx", meaning "lime." Calcite is a very common mineral. Clear calcite is used in special kinds of microscopes. FELDSPARThis name comes from the German word for "field" and "clip of wood." Feldspars are the most common of all minerals. Certain kinds are used in glass making, while others are set in jewelry. GALENAThis 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. GRAPHITEThis comes from the Greek word that means "to write." Graphite is the "lead" in pencils. HEMATITEThis comes from the Greek word for "blood", "haima." Hematite is the ore from which we get most of our iron. LIMESTONEThe word "lime" is related to a lot of other words-an old Greek word meaning "a moist meadow", Latin words meaning "mud" or "slime", and an Old English word "loam." There are many different kinds of limestone. Some of them have been used for hundreds of years to make cement and plaster. There is no connection between this word "lime" and the name for the green fruit. That "lime" comes from the same root as the Arabic word "laimun", which means both "lemon" and "lime." MAGENETITEThere is a place in ancient Greece called Magnesia. Magnets were first found there, and they were named "the Magnesian stone." Magnetite is a mineral that contains a great deal of iron and is strongly attracted to magnets; hence, its name. MARBLEThis name comes from the Greek word "marmaros", which means "shining stone." Marble is a metamorphic rock, formed naturally from limestone that is under great heat and pressure over a long period of time. It is often used as a building stone. OBSIDIANThis comes from the name of a man, Obsius, who was supposed to have found this rock in Ethiopia thousands of years ago. Obsidian is ancient volcanic glass and was once widely used for arrowheads. PUMICEThis volcanic rock was called pumax by the Romans. The name is related to their word for form, "spuma." Pumice is used for polishing hard things. QUARTZThis stems from the German word for "quartz"-"Quarz." Nobody seems to know where the German word came from. Quartz is an abundant mineral. Most sand is made up of small pieces of quartz. Quartz is important in glass making and in electronics. It is also used for sanding hard surfaces. SANDSTONESandstone is a sedimentary rock composed mostly of quartz grains cemented together. It is used as a building stone. SHALEThis is related to the word "scale", as in "fish scales", because shale occurs in flat layers. The name comes from an old German word meaning "shell." Shale is sedimentary rock; that is, it is formed from layers of mud which have been under pressure for a long time. SLATEThis comes from the Old French word "esclat", meaning "splinter" or "slat." Slate is a metamorphic rock formed from shale under great pressure. It is used for chalkboards and as a building stone. TALCThis word comes from the Latin word "talcum." In Old French, talc meant "mica", probably because some forms of talc occur in thin layers or plates like true mica. Talc is commonly used in talcum powder.