Tourmaline

Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. It is classified as a semi-precious stone and is known for its wide variety of colors.

Physical Properties

• Color: Tourmaline can occur in a wide range of colors, including black, blue, green, pink, red, yellow, and brown.
• Hardness: It has a hardness of 7 to 7.5 on the Mohs scale, making it suitable for jewelry and ornamental use.
• Crystal Structure: Tourmaline crystals are typically long and prismatic, with vertical striations on the surface.
• Cleavage: It exhibits no cleavage, and its fracture is conchoidal to uneven.

Formation and Occurrence

Tourmaline forms in various geological settings, including igneous rocks, metamorphic rocks, and in sedimentary environments through the alteration of pre-existing minerals. It is commonly found in granite and granite pegmatites, as well as in schist and marble.

Uses

Tourmaline is a popular gemstone used in jewelry, and it is also used as a semi-precious stone in ornamental objects. Additionally, it has applications in various industries, including as a component in pressure-sensing devices and in the production of infrared and ultraviolet light.

Study Guide

1. Describe the physical properties of tourmaline.
2. Explain the formation and occurrence of tourmaline.
3. Discuss the uses of tourmaline.
4. Identify and describe the different colors in which tourmaline can occur.
5. Examine the crystal structure and hardness of tourmaline.