Watermelon Tourmaline is a mineral with a hardness of 8 out of 10 on the Mohs scale of mineral hardness [?]. These Trigonally structured gems are made of complex borosilicate, their full chemical compound being Na(Li,Al)3Al6(BO3)Si6O18(OH)4.

Watermelon Tourmaline is a bi-colored/tri-colored/parti-colored occurrence of Tourmaline, and this appearance is usually a feature of the variety known as Elbaite. When cut parallel to its base, this tourmaline exhibits a rose-red center, a very thin colorless band parallel to the surface of the crystal, and a brown or green outer layer.

In parti-colored tourmaline the core is nearly colorless and outer segments may be pink in one end, green at the other end. Parti-coloured stones tend to be more fragile at the boundary areas of each color. In bicolored, the core is colorless or green and outer segments are pink. In some tricolored tourmaline, the color is separated in three zones: the core is frequently pink or red and the outer ends are white and green or any combination of these colors.

Color zoning giving the familiar watermelon appearance with the red core and green rind is brought about by more than one event in the genesis of the tourmaline crystal, including a change of composition during its growth. Colours that are visible in a single crystal range from pink to pale green, pale to deep blue (in the ordinary ray); in the extraordinary ray the crystals may show colorless to yellow, olive blue or purple.

All tourmalines have good resistance to weathering and are often found in alluvial areas, with mixtures of clay, sand, silt and gravel.

The finest elbaites come from Elba (Italy), the Urals (Russia), Sri Lanka, Namibia, Mozambique, Madagascar, Newry, Maine, and Pala, California (USA). In Nigeria, the pegmatites southeast of Keffi in western Plateau state have produced green, pink, red, violet, yellow and watermelon elbaite tourmalines. In Brazil it is known as Boco de fogo.

The specific gravity [?] for Watermelon Tourmaline is 3.06, it's refractive index [?] is 1.62-1.64, and it's double refraction [?] is 0.018.

History

Watermelon tourmaline takes its name from its concentrically-zoned appearance, typically red on the inside, and green on the outside, which when cut, looks like sliced watermelon.

Industrial Usages

Other varieties of tourmaline are maximized for their piezoelectric property. But colored and transparent varieties of elbaite tourmaline are widely sold as semiprecious stones.


The watermelon type of concentrically-zoned tourmaline material is often fashioned as thin, polished slabs for use in drop earrings and cuff-links.

You May Also Like...

Tugtupite

Tugtupite: Tugtupite is a mineral closely related to sodalite and hackmanite, all cyclosilicates whose structural silicate tetrahedrons are arranged in rings. It is also called beryllosodalite and reindeer stone, and crystallizes in the tetragonal system. It is found in fine-grained aggregates of crystals with its own distinctive cyclamen colour. Crystals are very small, tetragonal, almost cubic, or as shor (read full)

Zoisite

Zoisite: Zoisite is a hydrous calcium aluminum silicate in the Epidote group, with an orthorhombic crystal system, three crystal axes at right angles to each other, all of varying lengths. It appears in elongated, prismatic crystals, with fine parallel lines on the prism faces and usually poorly terminated. It also appears frequently in formless grains, poorly-defined crystals, rodlike aggregates and gran (read full)

Tags

Terms

Double Refraction or dr is the ability of a mineral to separate a refracted ray of light into 2 rays. If held over an image or text it will display the object 2x its original size.

Mohs Scale of Mineral Hardness is the standard used to categorize a mineral's ability to resist scratching. It gets its name from Friedrich Mohs, the German geologist who first created the scale.

RI or Refractive Index defines light's ability to move through the mineral or in a general sense, any material.

SG or Specific Gravity is the ratio of the weight of any substance to that of pure water at temperature of 3.98°C(39.2°F) and standard atmospheric pressure. This is important to note when actively seeking these minerals in the wild. Minerals with a higher SG will settle below material with a lower sg over time.