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
Stone City, Iowa Stone City, Iowa Stone City is an unincorporated community and census-designated place in Jones County, Iowa, United States. Stone City began as a company town for the workers of the local quarries. Stone City is known for its Anamosa Limestone quarries, historic limestone architecture, and 1930's art colony. Stone City was founded in 1850 along the banks of the Wapsipinicon River. Early settlers discovered dolomite limestone at the location. In its earliest history Stone City was known as the Anamosa Quarries. Later the area became known as the Stone City Quarries. In the late 1800s, Henry Dearborn, John Green, and