schorl tourmaline

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Description

schorl tourmaline is best known as “Black Tourmaline”. Although other forms of Tourmaline may be black, Schorl is exclusively black and, unlike other Tourmaline forms, is never transparent or even translucent.
Schorl is the most common form of Tourmaline. It may be highly lustrous and form in beautiful crystals, and is one of the most aesthetic black minerals known. see minerals.net for more

Mineral Group  silicate
Composition  Na(Mg,Fe,Li,Mn,Al)3Al6(BO3)3.O18(OH,F)4
dimension (cm)  4x3x3
weight (g)  60
It is a highly complex mix of several elements, especially sodium, aluminium, magnesium and iron, with a varying composition.
Background
The latest European arrival of all precious stones which are in current use. It was not until the beginning of the 18th century that tourmaline was brought from Sri Lanka (then Ceylon) by Dutchmen. Its name comes from the Sinhalese turamali (`stone attracting ash’): the stone has a very strange characteristic that was incomprehensible in those days. When heated, it attracts ash from the fire. Today, it is known that this is due to electricity, which originates in tourmaline because of its exceptional internal structure. When heated, the columns of tourmaline are charged positively at one end and negatively at the other. This phenomenon is called the pyroelectric capability of tourmaline.
The Sri Lanka variety is reddish to vividly red (rubellite). The less conspicuous black (schorl) was known long before the Sri Lanka variety. European miners and stoneworkers were familiar with schorl in many localities, but its dull colouring did not arouse their curiosity. No one ever conceived that the pink turamali of Sri Lanka and the black schorl were an identical mineral.
The diversity of colour made tourmaline popular as a precious stone in ancient times. It is possible to judge from excavations and written descriptions that it was favoured highly in the past. But it was so often mistaken for other minerals that gradually it fell into oblivion and by the Middle Ages it was again quite unknown in Europe.
Chemically it is one of the most complex minerals and its composition varies, for its different components can intermingle and replace each other: this, of course, makes tourmaline far more varied in colour than other minerals. Schorl is the most common variety, whereas the colourless achroite is the rarest one.
see geology.com for more

Additional information

Weight 60 g
Dimensions 4 x 3 x 3 cm