Gemstone value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone. Heat can improve gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is a common practice. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in “ametrine” – a stone partly amethyst and partly citrine. Aquamarine is often heated to remove yellow tones, or
J. F. S. Stone 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 ditch fill, he also found a piece of