Howlite

Howlite is a rarely occurring mineral from the mineral class of " borates " (formerly " silicates and Germanates ", see Classification ). It crystallizes in the monoclinic crystal system with the chemical composition of Ca2 [ B3O4 (OH ) 2 • OSiB2O4 (OH ) 3] and usually develops bulbous, low one and massive aggregates that are either colorless or white to beige. Rarely developed Howlite also tabular crystals, pointing to the crystal faces a vitreous luster.

Howlite is used exclusively for gemstones.

Special Features

Howlite is frequently crossed by black veins brown, similar in marbling of the coveted matrix turquoise. In the crystal surfaces shows vitreous luster, the fracture surfaces, however, are dull. Howlite conchoidal breaks like glass.

Howlite the magnesite ( magnesium carbonate a ) is very similar in appearance and can often be distinguished only by a chemical analysis of this. Howlite " melts " under the action of hydrochloric acid to a kind of gel, magnesite, however, responded by gas development. A density determination for distinguishing the two is often not enough, because Howlite is very similar with a density 2.5 to 2.6 g / cm ³ the magnesite ( 2.9 to 3.1 g / cm ³). In addition, magnesite is due to air inclusions often even easier.

Etymology and history

Was first found Howlite and described in Brookville at Windsor (Canada) 1868 by James Dwight Dana, who named the mineral after the Canadian chemist, geologist and mineralogist Henry How ( 1828-1879 ).

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the howlite mineral belonged to the class of " silicates and Germanates " and then to the Department of " chain silicates and phyllosilicates ( inosilicates ) ".

The valid since 2001 and used by the IMA 9th edition of the Strunz'schen Mineral classification assigns the howlite in the now independent class of " borates " and there in the department of " Triborate " one. This division, however, is further subdivided by the structural configuration so that the mineral in accordance with the subdivision " chain & ribbon ( Ino ) Triborate " is to find where it forms the unnamed group 6.CB.20 the only member.

The classification of minerals according to Dana assigns Howlite in the common class of " carbonates, nitrates and borates " and there in the department of " water clear borates with hydroxyl or halogen". He is the only member of the unnamed group 25/03/05 within the subdivision " Anhydrous borates with hydroxyl or halogen".

Education and Locations

Howlite is formed hydrothermally and is found mainly in borate deposits. In paragenesis, where he occurs among others, colemanite, ulexite and Bakerit.

Worldwide, Howlite so far (as of 2010) are detected in about 30 localities. Apart from its type locality Brookville at Windsor, he was still found in Canada on Cape Breton Island. In Germany he joined, among others, on Kohnstein (Thuringia) and in Rehden (Lower Saxony) to light.

Furthermore Howlite could to the localities Mesa del Almo at Aguja and in the borate deposit at La Salada ( Tubutama ) in the state of Sonora in Mexico; Bela Stena in Serbia in the Belgrade district; Gemerská Poloma ( Okres Rožňava, Košice ) in Slovakia; " Bigadiç Mine" in the Turkish province of Balıkesir, as well as in several regions of the U.S. states of California and Nevada be found.

Crystal structure

Howlite crystallizes in the monoclinic space group P21 / c with lattice parameters a = 12.82 Å; b = 9.35 Å; c = 8.61 Å and 104.8 ° and β = 4 formula units per unit cell.

Use as a gemstone

Howlite is a popular, but due to its low Mohs hardness of 3 to 3.5 very soft gemstone and therefore must be protected from damage to protect against daily usage by stabilizing ( coating of resin or plastic).

Manipulation and imitation

Since the magnesite the howlite looks similar, but is more common and therefore cheaper, it is often mistakenly sold as howlite. Both are, however, dyed blue, as imitation of the rare and valuable matrix turquoise.

Esoteric

In the esoteric Howlite is said to have a particular psychological and physical effects, but for which there is no scientific evidence to date.

So it should strengthen inter alia, the judgment and memory, relieve stress, pain and feelings of anger, neutralize negative energy and release blockages. Howlithwasser will generally have a positive effect on problems with bones, teeth, joints and nails.