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Boracite Hilgardite & Magnesite

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RSL754817

Boracite Hilgardite & Magnesite

Classic Locality

Description Tabs

Description
Locality: 
Boulby Mine, Loftus, North Yorkshire, United Kingdom
Class: 
Crystals on Matrix
Size Range: 
Miniature (4.5-7 cm)
Size: 
5 × 4.6 × 4.4 cm
Largest Crystal: 
0.50cm
Description

Specimens of boracite from this English mine show a pale bluish tone, with complex forms of the tetrahedron, modified by the cube and the dodecahedron, and stepped growths. Between transparent to translucent. They are accompanied by colorless hexagonal tabular crystals of magnesite and aggregates of reddish-colored hilgardite crystals. Boracite shows reddish hues due to hilgardite inclusions.
Both boracite and hilgardite, are magnesium and calcium chloroborates respectively. This mine, which is located east of Loftus, near Easington, is worked to obtain sodium and potassium salts. When miners find veins of these borates, the rock becomes very hard, which is a problem for exploitation and a joy for collectors. This English mineral classics are not usual in the market.

Mineral Data
What's on the rock

Boracite

Formula: 
Mg3(B7O13)Cl
Strunz: 
6.GA.05
Crystal System: 
Orthorhombic
Hardness: 
7.0 - 7.5
Streak: 
White
Type Locality: 
Lüneburger Kalkberg, Lüneburg, Lower Saxony, Germany

Hilgardite

Formula: 
Ca2B5O9Cl·H2O
Strunz: 
6.ED.05
Hardness: 
5.0
Streak: 
White
Type Locality: 
Choctaw Salt Dome (Bayou Choctaw Salt Dome), Plaquemine, Iberville Parish, Louisiana, USA

Magnesite

Formula: 
MgCO3
Strunz: 
5.AB.05
Crystal System: 
Trigonal
Hardness: 
3.5 - 4.5
Streak: 
White
Type Locality: 
Magnisía Prefecture (Magnesia), Thessalia Department (Thessaly), Greece