Schorl

Schorl is a mineral species belonging to the tourmaline group. It is the most common variety of tourmaline found in nature, often forming in igneous rocks and metamorphic rocks. Schorl is characterized by its black color, vitreous luster, and prismatic crystal habit.

Characteristics

Schorl is a complex boron silicate mineral with a general formula of NaFe3Al6(BO3)3Si6O18(OH)4. It is distinguished by its black color, which is caused by the presence of iron in its structure. The mineral has a hardness of 7-7.5 on the Mohs scale, making it relatively hard and resistant to scratching. It exhibits a vitreous luster and forms in prismatic crystals, often with striations running along the length of the crystal.

Occurrence and Formation

Schorl is the most common variety of tourmaline and can be found worldwide. It is often associated with quartz and feldspar in igneous rocks such as granite and pegmatite, as well as in metamorphic rocks like schist and gneiss. Schorl forms under a wide range of temperature and pressure conditions, but it is particularly common in high-temperature hydrothermal veins and in cavities in granitic rocks.

Uses

While schorl is not typically used as a gemstone due to its dark color, it is often collected by mineral enthusiasts for its distinctive crystal habit and luster. In addition, schorl has been studied for its potential use in piezoelectric applications, due to the electric charge it generates under mechanical stress.

See Also

• Tourmaline
• Boron
• Silicate minerals
• Igneous rock
• Metamorphic rock