Colorless quartz are irradiated and heat-treated to become greenish, yellowish, and brownish for the jewelry industry. Only a small fraction of natural, colorless quartz can develop colors through this process. The identification of this quartz is made through irradiation and heat-treatment tests on representative samples. The samples are sent to irradiators and then heat-treated. These tests are not fast enough for the needs of the semiprecious dealers. A new test is presented, that avoids irradiation and heat-treatment. It can identify samples with potential to develop colors in a few minutes. If a portable infrared spectrophotometer is available, it can be performed in field.
quartz; irradiation; color; infrared
