Boronite

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Bornite (deep-bornite), also known as bunt copper kies, copper laser ore or copper lazur, is a common mineral from the mineral class of “sulphides and sulfo salts”. It crystallizes in the orthorhombic crystal system with the chemical composition Cu5FeS4 and develops mostly massive aggregates, rarely crystals in octahedral or pseudocubic form in bronze or copper color.

Etymology and History

Bornit had been known since 1725, but its official name was only given in 1845 by Wilhelm Ritter von Haidinger, who named the mineral after the Austrian mineralogist Ignaz von Born. Its mining name Buntkupferkies received the mineral because it very quickly forms colorful tarnish colors in air.

Typical locality is Jáchymov (German Sankt Joachimsthal) in the Czech Republic.

Classification
Already in the obsolete system of minerals according to Strunz (8th edition) #II/A. Sulfides etc. with M : S > 1 : 1|8. Edition of the mineral systematic according to Strunz]], the boronite belonged to the mineral class of the “sulphides and sulfo salts” and there to the division of the “sulphides etc. with [the molar ratio] M(etall) : S(chwefel) > 1 : 1”, where together with digenite he formed the “digenite-bornite group” with the system no. II/A.02 and the other member Anilith as well as in the appendix with rickardite and umangite.

In the latest Lapis Mineral List according to Stefan Weiss, revised and updated in 2018, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz’s systematics, the mineral received the System and Mineral No. II/B.02-30. In the “Lapis Systematic”, this corresponds to the more precisely defined division “Sulfides, selenides and tellurides with [the amount of substance] ratio of metal: S,Se,Te > 1 : 1”, where boronite together with betechtinite, gortdrumite and calvertite forms the group “Complex copper-iron-sulphides”.

Valid since 2001 and last updated by the International Mineralogical Association (IMA) in 2009 #B Metallsulfide, M : S > 1 : 1 (mainly 2 : 1)|9. Edition of Strunz's Mineral Systematics also classifies the boronite into the department of "Metal sulfides, M : S > 1 : 1 (mainly 2 : 1)". However, this is further divided according to the metals predominant in the compound, so that the mineral is found according to its composition in the subdivision "with copper (Cu), silver (Ag), gold (Au)", where it is the only member of the unnamed group 2.BA.10.

The system of minerals according to Dana, which is mainly used in English-speaking countries, also classifies the boronite into the class of "sulphides and sulfo salts" and there into the division of "sulphide minerals". Here he is the only member of the unnamed group 02.05.02 within the subdivision of the “Sulfides” – including selenides and tellurides – with the composition AmBn