Schorl

Schorl is the black, iron-rich species of tourmaline and by far the most common tourmaline in nature, making up the great majority of all tourmaline found. The opaque black color comes from its high iron content. It is the mineral most people mean when they say black tourmaline.

Schorl forms striking long prismatic crystals with deeply striated faces and a rounded triangular cross-section. Crystals are often found embedded in granite, pegmatite, or quartz, and aesthetic schorl-in-quartz pieces are popular.

Unlike the gem-quality elbaite varieties, schorl is rarely transparent or faceted; it is valued instead as crystal specimens and as a widely used metaphysical stone.

Schorl forms in granitic pegmatites, granites, and metamorphic rocks such as schist and gneiss, crystallizing where boron is available and iron is abundant in the fluids. Its tolerance for iron-rich conditions makes it the most widespread tourmaline.

It frequently grows alongside quartz, feldspar, and mica, and is a common accessory mineral in many granites. In pegmatite pockets it can occur with gem tourmalines, beryl, and other minerals.

Schorl is found worldwide, with notable specimens from Brazil, Namibia (often with aquamarine), Pakistan, Afghanistan, Madagascar, and the United States.

Look for opaque black prismatic crystals with strong lengthwise striations and a characteristic rounded triangular cross-section. Hardness is 7-7.5 with vitreous luster and a grayish-white streak (the crystal is black but the streak is not).

Schorl has no cleavage, which helps separate it from black minerals like hornblende and tourmaline-like rods of other species. Unlike magnetite, schorl is not magnetic and is harder. Black obsidian is glassy and breaks conchoidally without crystal form.

The striated triangular prisms are the most reliable field clue. Schorl is pyroelectric and piezoelectric, developing a charge when heated or stressed, a classic tourmaline property.

Schorl is mainly collected as mineral specimens, especially attractive crystals in quartz or feldspar matrix. It is the workhorse of the metaphysical market as black tourmaline, sold as raw chunks, tumbled stones, and points.

Industrially, tourmaline's piezoelectric and pyroelectric properties have been used in pressure gauges and other devices, and powdered tourmaline is marketed in various consumer products. Schorl is not generally used as a faceted gem because it is opaque.

Metaphysically, black tourmaline (schorl) is one of the most popular protection and grounding stones, said to shield against negativity. These claims are traditional rather than scientific.