Description
Smoky quartz is a variety of quartz. Its color ranges from smoky brown to almost black, translucent. Very dark varieties are called morion. Smoky quartz is most common in cavities in intrusive rocks and high-grade metamorphic rocks. It is rare in sedimentary and effusive rocks. Localities include the Alps, Brazil, Russia, Mexico, India, Ireland, Zimbabwe, Afghanistan, and the United States. The color of smoky quartz is caused by aluminum in the crystal lattice combined with ionizing radiation. The aluminum replaces the silicon in the crystal structure, forming the complex [AlO4-] instead of [SiO4]. To compensate for the resulting charge difference, small monovalent cations such as hydrogen, lithium, or sodium are simultaneously incorporated into the crystal structure during crystal growth. Under the influence of ionizing radiation, the electron of the [AlO4-] complex moves to a cation, creating a color center. This process normally only occurs below 50°C. At higher temperatures, the breakdown of the color centers occurs faster than their formation. The source of the ionizing radiation is usually potassium-40 from the surrounding rock. The color of smoky quartz therefore develops long after the crystals have formed and can take several million years. This is also why most smoky quartz forms in feldspar-rich rocks such as granite. When heated above 200°C, smoky quartz will lose its color. Irradiating clear quartz (rock crystal) with X-rays or gamma rays almost always produces smoky quartz. This method is therefore used to create smoky quartz from colorless quartz. In ancient times, this stone warned soldiers in battle if it darkened. Smoky quartz is still used today for rosaries and crucifixes. Smoky quartz is attributed with several medicinal properties; it is said to help with digestive problems, stress, grief, and assist with conceiving. According to various literature, the mineral belongs to the zodiac sign: Libra.
