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
GemStone IV 1995, just after the de-ICEing process. It had already become available on CompuServe and Prodigy before that. When AOL switched to flat-rate pricing, "GemStone" did over 1.4 million customer-hours in a single month and was attracting 2,000-2,500 simultaneous players. Simutronics launched a web portal in 1997, and started phasing customers off of the online services and onto the web interface, although it would take several years before the last of the online service portals were closed. "Computer Gaming World" in 1991 stated that "Gemstone III" was a good example of the best and worst aspects of online play. The reviewer