Kyanite

Kyanite "with standing surface" Found in the far north of Brazil.

Natural Agate POLISHED PIECE on standard from the mines in Brazil.

Natural Agate POLISHED PIECE on standard from the mines in Brazil.

Tourmaline -sometimes with mica crystallizations on it- "with standing surface" found in Brazil.

Nice little affordable Tourmaline pieces with flat side, so it can stand up easily!
Availability: In stock
SKU
10779
  • Buy 10 for €39.00 each and save 20%
Tourmaline -sometimes with mica crystallizations on it- "with standing surface" found in Brazil. is available to buy in increments of 3

Tourmaline (quartz) is a group of minerals, all cyclosilicates. The minerals in this group share a characteristic chemical formula: AX3Y6 (BO3) 3 Si6O18 (O, OH, F) 4. The A can contain calcium or sodium. The X can be aluminum, iron, lithium or magnesium. The Y is normally aluminum, but can also be chrome or iron. There may be some potassium in the position of A, manganese may be in X, and vanadium may be found in Y, but these elements are not common in the tourmaline group formulas. Tourmaline is found in pegmatites, metamorphites, magmatites and alluvial deposits. Although tourmaline was known in ancient times in the Mediterranean, it was only imported from Sri Lanka by the Dutch into Western Europe in 1703. They named the new gem with a Sinhala word "Turmali", which means "stone with mixed colors". Rubellites were traditionally used as gemstones - they were used by artists as a talisman, because they would increase the creativity of artists. Tourmalines have certain unique properties. They are piezoelectric, meaning that when a crystal is heated or compressed, different electrical charges are formed at both ends of the crystal. This creates an electric potential. When an external electrical potential is applied to the crystal, it vibrates. The minerals are pleochroic, meaning that the crystal is darker in color when viewed along the longest axis of the crystal than when viewed perpendicular to that axis. The four best known and most common tourmaline minerals have different colors and transparencies. Elbaite is transparent and a valuable gemstone. Schorl, which is rich in iron, is the most abundant mineral of the tourmaline group and is black and opaque. It is mainly formed in pegmatites, the extremely slowly cooling gangue rocks of a magma. The two other regular tourmalines are dravite and uvite. Dravite is usually translucent brown and can grow very large. Uvite is green translucent to opaque. Tourmaline occurs in the sand fraction of Dutch Quaternary river sediments. It is, among other things, a characteristic component of Maas sands. In the heavy mineral analysis as it took place in the Netherlands at the National Geological Survey during the second half of the twentieth century, the mineral is classified in the so-called stable group.

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Dimensions 0.4-4kilo
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