Gemstone the stone such as color zoning (the uneven distribution of coloring within a gem) and asteria (star effects). The Greeks, for example, greatly valued asteria gemstones, which were regarded as powerful love charms, and Helen of Troy was known to have worn star-corundum. Aside from the diamond, the ruby, sapphire, emerald, pearl (not, strictly speaking, a gemstone), and opal have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a "precious stone" as well, going back to ancient Greece. Even in the last century certain stones such
Gregory S. Stone Gregory S. Stone Gregory Schofield Stone (born 1957 in Boston, Massachusetts) is an ocean scientist, explorer, and marine conservationist. He has published research on marine mammals in Antarctica, on ice ecology. and on New Zealand's Hector's dolphin. Stone is also an undersea technology and exploration specialist, particularly in his use of deep-sea submersibles, and has produced a series of marine conservation films. Stone earned a Bachelor of Arts degree in human ecology from the College of the Atlantic in 1982. He earned his master's degree in marine policy from the University of Rhode Island in 1989; and earned a Ph.D.