Green Tourmaline Crystals 4 Pieces Raw Minerals Stones Rocks Collecting

Description

Origin : Afghanistan

Size : 3k - mm 8-17

Lot 4 Pieces Green Tourmaline Natural Crystals Gem 3 carats mm 8-17 Raw Minerals Stones Rocks for Collection, as in photo.
Color: green;
Treatments/enhancements: none.
The stone has a high degree of facet, the color is very good as well as the form, so good to be cut, the cost of which is amply repaid, although lately prices have risen over the past years up to 500%, especially for best quality stones above the 1-2 carat, as their Afghan counterparts are less and less faceted due to excessive mining the past 50 years which is leading to exhaustion of the mineral.

Available in single crystals or lots, tumbled, pendant or worked gems, at this link.
Also available Black Tourmaline in tumbled form, rough or polished pendant, small rough crystals of various shapes, also in lot and in plexiglas box, at this link.
Also on sale are Pink Tourmaline and "Watermelon" Tourmaline Crystals.

Tourmalines are a group of minerals belonging to the class of silicates, order of cyclosilicates.
The name comes from the Sinhalese turmali which means stone of various colors.
The crystal belongs to the trigonal system, it is prismatic, very elongated, vertically striated and sometimes with unequal development at the two ends of the vertical axis.
There are polychrome varieties in which the color varies both in concentric areas and in the direction of crystal elongation. You can mainly find red, pink, blue, green and yellow tourmalines.
Tourmaline is a common accessory mineral in igneous and metamorphic rocks and is abundant in pegmatites; due to their hardness and inalterability they can also be found in sedimentary rocks.
The most beautiful clear varieties come from the island of Elba, Brazil, the Urals, Madagascar, Sri Lanka, Namibia, Mozambique, Maine and California in the USA.
Tourmalines are endowed with pyroelectricity (they charge electrically if first heated and then cooled) and piezoelectricity (they charge electrically if subjected to pressure). They are resistant to acids.
The silicon is placed at the center of a tetrahedron whose vertices are the oxygen atoms. The tetrahedra are joined to each other by two vertices in groups of six.