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
J. F. S. Stone C "Stonehenge Complete" (Thames and Hudson, London, 2004) J. F. S. Stone John Frederick Smerdon Stone (1891? – 1957) was a British archaeologist, most famous for his work in and around Wiltshire, especially at Stonehenge and the Woodhenge area. In 1947, Dr Stone excavated the first ever trench across the Stonehenge cursus, at a site near the Fargo Plantation a little north west of the stone circle. This permitted its dating for the first time and Dr Stone was able to establish its prehistoric date and that it had been constructed using antler picks in irregular sections. In the cursus