Achroite
is the colorless variety of Tourmaline, that
is usually, but not always, the Elbaite
variety of Tourmaline.
The absence of color may
be due to the presence of Manganese (Mn) and/or Magnesium
(Mg). Achroite crystals
typically have well developed faces, are elongated and striated with triangular cross
sections and pyramidal terminations. Crystal often
appear fibrous or heavily included. Clean, clear, colorless
crystals large enough for faceting are very rare. Crystals
can be multi-colored from some locations. The most common
secondary color is green. Some crystals are colorless
at the base and termination with various shades of green
in the middle. Other crystals are green at the termination
and colorless at the base, etc. Some Achroite gems may
have a very slight hint of pink and others may
be heated to remove the pink. As with other Tourmaline
varieties, Achroite is Piezoelectric
and Pyroelectric.
Achroite
was named in 1845 by Russian chemist Rudolph Hermann (1805-1879)
from the Greek word
άχρους (áchrous),
meaning colorless or without
color.
In 1855 Hermann developed his own classification
of minerals which he named heterodimensional. The Vernadsky
State Geological Museum in Moscow keeps the mineralogical
collection of Hermann, totalling more than 3000 samples
of 900 mineral species and varieties from Europe, Russia
and America. Hermann also discovered Chiolite and also
analysed and named Planerite, Pyrophyllite and Turgite.
Achroite
distribution: the best Achroite crystals may be from
the Paprok Mine, Kamdesh District, Nuristan Province, Afghanistan.
At Usakos, Karibib District, Erongo Region, Namibia.
At Skardu, Skardu District, Baltistan, Gilgit-Baltistan, Pakistan.
In the USA at the Mountain Lily Mine, Aguanga Mountain, Oak Grove, Aguanga Mountain District, San Diego County, California.
Achroite has also been reported from Bolivia, Czech Republic, England,
India, Madagascar, Nepal and Sri Lanka.
|