Quartz, which can split light into a spectrum, is one of the most common of all rock-forming minerals and one of the most important constituents of the earth's crust. Quartz may be transparent, translucent, or opaque; it may be colorless or colored. Varieties are classified as crystalline and cryptocrystalline, whose crystal structure can be seen only under the microscope, if at all. What is quartz's rank on the Mohs scale of hardness?
Louisa May Alcott
Back in the day
Elvis Presley is also known as "The King of Rock 'n' Roll." He became a national sensation in 1956 and dominated rock music until 1963. Among his most successful songs were "Heartbreak Hotel," "Love Me Tender," and "Don't Be Cruel." His success spawned a spate of B movie appearances, but his popularity waned in the late 60s after the "British Invasion." What facts do some fans cite in their claims that Elvis did not really die in 1977?
Born on a day like today
Kelvin was a British mathematician and physicist known especially for his work on heat and electricity. He introduced the Kelvin temperature scale, discovered the Thomson effect in thermoelectricity, and was an important innovator and authority in the field of message transmissions through submarine cables. He invented the siphon recorder, an instrument by which telegraphic messages are recorded in ink fed from a siphon, as well as the reflecting galvanometer, which measures what?