The most common occurrence of tourmaline is as an accessory mineral in igneous and metamorphic rocks. It often occurs as millimeter-size crystals scattered through granite, pegmatite, or gneiss. In this mode of occurrence, tourmaline rarely makes up more than a few percent of the rock’s volume. The variety of tourmaline most often found as an accessory mineral is…

Tourmaline has a Mohs hardness of 7 to 7 ½, and that hardness makes it a durable sediment granule. Tourmaline is also relatively resistant to chemical weathering. So, particles of tourmaline weathered from igneous or metamorphic rocks can persist in a stream and can be transported long distances from their source area. Tourmaline gem rough is mined…

Tourmaline most commonly occurs as an accessory mineral in igneous and metamorphic rocks. Large, well-formed crystals of tourmaline can form in cavities and fractures during hydrothermal activity. Tourmaline is a hard and tenacious mineral. That enables it to persist during stream and beach transport as durable grains in sediments and sedimentary rocks. Tourmaline Crystals The most spectacular tourmaline…

Tourmaline is the name of a large group of boron silicate minerals. These minerals share a common crystal structure and similar physical properties – but vary tremendously in chemical composition. The wide range of compositions and color zoning within crystals causes tourmaline to occur in more colors and color combinations than any other mineral group. Tourmaline is…