Minerals from Pakistan
.... Tourmaline.....

The name is derived from the singalese "Turamali" and means "mixed gems"

It crystallizes in the trigonal system with relatively simple elongated prisms with simple terminations. The prism faces are often striated parallel to direction of elongation (c axis). The rounded triangular cross-sectional shape of tourmaline crystals is typical of this mineral. The hardness is 7-7.5

The chemical formula is very complex, substantially it is a borum silicate of aluminum with iron and magnesium .

The colors are extremely variable, due to the presence of different metals in the composition: green ( Verdelite  or Chrome tourmaline), deep pink to red ( rubellite), black, due to iron presence ( schorl ), blue (indicolite), pink, due to Lithium , transparent no colored ( acroite ).  The most researched gem variety is Elbaite, from Elba island, in Italy.

Typical of the tourmalines are the polychromatic varieties,  that have different colors or zonations in the same crystal,; generally the zonations are perpendicular to the elongation of the crystals, giving a really fantastic aesthetic effect.

 Elbaites are richer in sodium than other tourmalines (Na(Li,Al)3Al6Si6O18(BO3)3(OH)4). They are the most valuable tourmalines frequently polychromes

A typical characteristic of this mineral is the piezoelectricity.

The  gem tourmaline is a typical mineral of pegmatites.

 Brazil is the most important source of this mineral. As usual the most important mines are in Minas Gerais, very important and famous are Galconda, Jonas, Cruzeiro. Important areas are also U.S.A., southern California (Pala, San Diego county, exceptional gem tourmalines normally bi-colored ), Maine ( Paris ), F.S.U., Madagascar, Tanzania ( exceptional green tourmalines, called chrome-tourmalines) ,Sri Lanka( from placers, with ruby and beryl ), Namibia, Afghanistan and Pakistan.

In Italy the most famous tourmalines are from the pegmatites of the Elba island, that gave the name to the variety Elbaite. Other tourmalines very common are shorl  in different areas, the most famous are from the gneiss quarries in Ossola Valley. New colored gem tourmalines are from a very recent find in the Adamello area.

Black tourmalines are also common in the pegmatite veins of Como Lake, Val Codera, Baveno, Cuasso al Monte.

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