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
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.