Boracite

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Boracite
Mg₃[Cl|B₇O₁₃]



Boracite was first described, from Lüneburg, Germany, by Lasius in 1787 as "cubic quartz" - an understandable mistake considering that the science of mineralogy was still in its infancy, that the element boron had not yet been discovered, and that boracite had certain physical properties close to that of quartz (vitreous luster, lack of cleavage, and a hardness that actually slightly exceeds that of quartz). Within a year or two after its original discovery, mineralogists realized that it couldn't be quartz because the chemistry was different, although the full composition (magnesium chloro-borate) was not recognized until 1850!


Boracite
Bolivia
Cochabamba Department, Chapare Province, Alto Chapare District,

Boracite on matrix 4.7cm wide	© Rob Lavinsky

Boracite crystal 1.3cm wide	© Rob Lavinsky

The eroded and slightly metamorphosed Cambrian or Precambrian saltdome caprocks exposed over several square kilometres of rainforest in the Alto Chapare region have become a prolific source of boracite. In the early 1940s, while investigating this then still roadless jungle for its asbestos deposits, Dr. Federico Ahlfeld found a solitary loose green cube in stream sand and sent it to Dr. Roberto Herzenberg, who destroyed it for wet chemical analysis. That remained the only known boracite crystal from the continent of South America for the next 50 years, until the early 1990s when the locality was rediscovered by Alfredo Petrov. Boracites here occur in many colours, mostly pale pastel shades (colourless, green, orange, pink, grey, exceptionally yellow); several crystal habits, most commonly pseudocubic, but also tetrahedral, and rounded combined forms; and in size range from microscopic up to the largest known crystals in the world (3.7cm). Typical pale green opaque to translucent cubes in the 1cm size range are so abundant that they should be readily available for less than $20. Aesthetic crystals around 1.5cm or more, or of colours other than light greenish, are hard to get and can be expected to cost a few hundred $$. Note that this is one of very few places in the world where boracite can be found on the surface, as opposed to underground in salt mines.


France
Luneville

There is no boracite here, although the locality has been mentioned several times in the paper literature as a boracite locality. Was probably originally a confusion with the name of the type locality - Luneburg - which has been uncritically copied as a boracite locality by several subsequent authors. Obviously shouldn't be included in a "best minerals" list, but we include this note just as a warning for future compilers of regional species lists.


Germany
Lower Saxony, Elze, Eime




Germany
Lower Saxony, Hanover, Lehrte



Germany
Lower Saxony, Lüneburg, Kalkberg Hill

Boracite crystal 8mm wide	© Volker Betz

A 1cm tetrahedral Boracite crystal on matrix	© Peter Haas

Boracite crystals largest ~7mm	© Jakub Jirásek

Lasius, G.S.O. (1787) Chemischen Annalen für die Freunde der Naturlehre, Arzneygelahrtheit, Haushaltungskunst und Manufacturen (Chemical Annals for the Friends of Natural History, Pharmacology, Home Economics and Manufacturing), #2, 333-336. - This publication constitutes the first description of boracite (then as "cubic quartz" ), making Lüneburg its type locality. The crystals immediately became a popular collectible, both among mineral collectors and among children who used them as dice, and they were even collected (and sold) by criminals who had been sent as punishment to labour in the gypsum quarry.
The largest crystals known from the type locality reached 3 cm size, but have since been lost. The largest currently preserved measures 1.7cm and is in a Lüneburg museum. It is no longer allowed to collect at the locality, but small crystals (2 to 5 mm) are often available on the market when old collections are recycled. Crystals of 1cm or more size are very rarely offered for sale.


Germany
Saxony-Anhalt, Bernburg

Boracite FOV 3mm	© O. Dziallas

Boracite FOV 1.2cm	© Peter Haas

Germany
Saxony-Anhalt, Stassfurt Potash deposit, Stassfurt



Germany
Thuringia, Sondershausen, Glückauf Mine




Poland
Kujawsko-Pomorskie, Inowrocław




United Kingdom
England, North Yorkshire, Loftus, Boulby Mine

© Rob Lavinsky

© Rob Lavinsky

USA
California, San Bernardino Co, Otis

"Boracite" was erroneously listed from here in a State publication in the 1930s, and this reference has appeared several times in the literature since then, uncritically copied by later authors. Was probably an error for borax or hydroboracite. Obviously shouldn't be included in a "best minerals" list, but we include this note just as a warning for future compilers of regional species lists.



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Edited 32 time(s). Last edit at 08/05/2010 03:28AM by Rock Currier.