Kunzite pocket stone / flat stone from Afghanistan.

Kunzite pocket stone / flat stone from Afghanistan.

Fluorite trailer from the UK, very special and unique type of Fluorite.

Fluorite trailer from the UK, very special and unique type of Fluorite.

Black Tourmaline also called Schörl Tourmaline semi flat stone / pocket stone from Brazil

Not rare, but a very difficult stone to sharpen a flat stone because of it. it quickly tears its many fracture / splitting surfaces when grinding. Once cut, the stone is resolute and strong.
Availability: In stock
SKU
10673
Black Tourmaline also called Schörl Tourmaline semi flat stone / pocket stone from Brazil is available to buy in increments of 1

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. The position of A may have some potassium, manganese may be in X and vanadium may be found in Y, but these elements are not common in 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 Sinhalese 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 very slowly cooling gangue rocks of a magma. The two other tourmalines that regularly occur are dravite and uvite. Dravite is usually brown translucent 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 Service during the second half of the twentieth century, the mineral is classified in the so-called stable group.

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