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
George Stone (bishop) that nobleman became Lord Lieutenant of Ireland in 1731. In 1733 Stone was made Dean of Ferns, and in the following year he exchanged this deanery for that of Derry. In 1740 he became Bishop of Ferns and Leighlin, in 1743 Bishop of Kildare, in 1745 Bishop of Derry, and in 1747 Archbishop of Armagh. During the two years that he occupied the See of Kildare he was also Dean of Christ Church, Dublin. From the moment that he became Primate of All Ireland, Stone proved himself more a politician than an ecclesiastic. "He was said to have been selfish,