Gemstones
The Earth hosts an immense variety of precious gemstones, found deep within its layers at various depths. Many gemstones form from a combination of minerals consisting of two or more elements. Silicon dioxide serves as a primary component in these gemstones alongside certain mineral impurities. The composition, conditions, and elements that constitute gemstones can vary greatly, making it challenging to encompass all types in a single discussion. However, we will focus specifically on tourmaline stones.
Tourmaline Stone
Tourmaline is classified as a semi-precious stone and consists of a crystalline structure comprised of boron, several silicate minerals, and a variety of elements including potassium, sodium, aluminum, iron, lithium, and magnesium. This mineral is generally non-piezoelectric at specific temperatures, but exhibits electrical properties when subjected to extreme heat or cold. In terms of hardness, tourmaline ranks seventh on the Mohs scale, indicating its robustness relative to other gemstones.
Tourmaline is available in numerous colors, with black being the most predominant. In the 19th century, chemists utilized this type of gem in experiments involving light attraction, as its polished surface effectively concentrated rays. Physically and chemically, tourmaline is characterized by its white streak, uneven fracture pattern, and a specific gravity of approximately 3.06. Notably, it displays distinct optical properties such as birefringence, possesses a single negative axis, and crystallizes in a trigonal system.
History of Tourmaline
Tourmaline is believed to have originated in Sri Lanka. During the colonial era, several companies with Indian and Dutch origins imported large quantities of this gemstone to Europe to satisfy growing demands among gemstone enthusiasts. Notably, scientist Johan S. Rubens discovered that the mineral identified in 1703 was, in fact, tourmaline, and not zircon as previously thought.
Types of Tourmaline
- Schorl: This type is characterized by a black or dark brown hue.
- Dravite: Features dark yellow shades leaning towards brown-black.
- Elbaite: Known for its red or reddish-pink varieties.
- Light blue with greenish tints.
- Verdelite: Recognized for its green color.
- Achroite: This variety is colorless.