Moissanite

Moissanite was introduced to the jewelry market in 1998 after Charles & Colvard (formerly known as C3 Inc.) received patents to create and market lab-grown silicon carbide gemstones, becoming the first firm to do so. By 2018 all patents world-wide had expired. Charles & Colvard currently makes and distributes moissanite jewelry and loose gems under the trademarks Forever One, Forever Brilliant, and Forever Classic. Other manufacturers market silicon carbide gemstones under trademarked names such as Amora. In many developed countries, the use of moissanite in jewelry was controlled by the patents held by Charles & Colvard; these patents expired in August 2015 for the United States, 2016 in most other countries, and 2018 in Mexico. Moissanite is regarded as a diamond alternative, with some optical properties exceeding those of diamond. It is marketed as a lower price alternative to diamond that also claims less exploitative mining practices. As some of its properties are quite similar to diamond, moissanite can be used for scams. Testing equipment based on measuring thermal conductivity in particular may give deceiving results. On the Mohs scale of mineral hardness moissanite is rated as 9.5, with diamond being 10 (by definition). In contrast to diamond, moissanite exhibits a thermochromism, such that heating it gradually will cause it to change color, starting at around 65 °C (150 °F). A more practical test is a measurement of electrical conductivity, which will show higher values for moissanite. Moissanite is birefringent, which can be easily seen, and diamond is not. Because of its hardness, it can be used in high-pressure experiments, as a replacement for diamond (see diamond anvil cell). Since large diamonds are usually too expensive to be used as anvils, moissanite is more often used in large-volume experiments. Synthetic moissanite is also interesting for electronic and thermal applications because its thermal conductivity is similar to that of diamonds. High power silicon carbide electronic devices are expected to find use in the design of protection circuits used for motors, actuators, and energy storage or pulse power systems. It also exhibits thermoluminescence, making it useful in radiation dosimetry.