Datolite

• Calciumboratosilikat
• Prismatic Distomspat

Datolith is a mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the composition CaB [ OH | SiO4 ], and is therefore in chemical terms, a calcium -boron silicate, or more precisely a Calciumboratosilikat with hydroxide ions as additional anions.

Datolith developed kurzsäulige or dicktafelige crystals of up to 12 centimeters in length, but is often found in the form racemose to spherical, granular or massive mineral aggregates. Uninjured or unweathered crystal faces have a glass-like luster, fracture surfaces shimmer, however rather weak resin similar. In its pure form Datolith is colorless and transparent. But it can also appear white and accept by foreign admixtures a gray, yellow, green or pink to red color, the transparency decreases correspondingly by multiple refraction due to lattice defects or polycrystalline training.

Special Features

Before the blowpipe Datolith melts with effervescence to a clear bead and colors the flame green. In hydrochloric acid it assumes a gelatinous consistency.

Under short-wave UV light, show some Datolithe blue fluorescence.

Etymology and history

The name Datolith is composed of the Greek word δατέομαι [ detéomai ] " share or distribute " and for λίθος [lit ʰ os] for " stone " and refers to a willing divisibility of the often occurring friable mineral aggregates.

First discovered and described the mineral in 1805 by Jens Esmark ( 1763-1839 ) in the pit " Nødebro " at Arendal in Norway's Fylke ( province ) Aust- Agder.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Datolith belonged to the department of " island silicates with tetrahedral foreign anions ( Neso - Subsilikate ) ", together with Bakerit, Calcybeborosilit - (Y), Gadolinit - (Ce) where he, Gadolinit - (Y), Hingganit - (Ce), Hingganit - (Y), Hingganit - (Yb ), and Homilit Minasgeraisit - (Y) the " Datolith - Gadolinit group " with the system no. VIII/B.29 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Datolith also in the department of " island silicates ( nesosilicates ) ". However, this is further subdivided according to the possible presence of other anions and the coordination of the cations involved, so that the mineral according to its composition in the subsection " island silicates with BO3 triangles and / or B, Be tetrahedra eckenteilend with SiO4 " can be found where it, together with Bakerit, Calcybeborosilit (Y ), gadolinite ( Ce), gadolinite - (Y) Hingganit ( Ce), Hingganit - (Y) Hingganit ( Yb), Homilit, Melanocerit ( Ce) and Minasgeraisit - (Y ) is the unnamed group 9.AJ.20.

The mainly common in English-speaking classification of minerals according to Dana assigns the Datolith in the fine already divided the department " Inselsilkate: borosilicates and some Beryllosilikate with (BO3 ) " a. Here he is as the namesake of the " Datolithgruppe ( Datolith series) " with the system no. 54.02.01a and the other members Hingganit - (Ce), Hingganit - (Y), Hingganit - (Yb ) and Calcybeborosilit - (Y ) within the subdivision " Inselsilkate: borosilicates and some Beryllosilikate with B in co-ordination " to be found.

Modifications and varieties

Botryolith (also Faserdatolith ) is a racemose variety of Datolith.

As Haytorit a pseudomorph of Chalcedon after Datolith is called.

Education and Locations

Datolith either forms in metamorphic rocks or by hydrothermal processes, but is also found in volcanic rock, on veins, in pegmatites or Amethyst inside of Chalcedonkugeln. Accompanying minerals occur among others Axinit, calcite, Danburite, grenade, prehnite, zeolites.

As rarely occurring mineral formation Datolith can indeed be abundant in part to different sites, overall he is not very common. Are known so far (as of 2012) about 460 localities. Found the mineral was, among others, on the following sites: Tasmania ( Colebrook Hill ) in Australia; Hubei, Yunnan and Zhejiang in China; in many regions of Germany (including St. Andrew Berg and Lower Churches ( Westpfalz ) ); Alsace and Lorraine in France; England and Scotland in the United Kingdom; Italy; Hokkaidō, Kyūshū undShikoku Japan; Kazakhstan; Ontario (Hastings County) and Quebec ( Argenteuil County) in Canada; Meknès- Tafilalet and Souss -Massa- Daraâ in Morocco; Guanajuato and San Luis Potosí in Mexico; Namibia ( Omaruru ); New Zealand (North Iceland ); North Korea; among other Magneterzlagern in gneiss at Arendal in Norway; Salzburg ( Hohe Tauern ), Styria ( Eibegggraben ) and Tyrol ( Tauerntal, Tisza ) in Austria; Poland; some regions in Russia; Sweden; Switzerland ( Grischun and Wallis ); Slovakia; Spain; South Africa; Tajikistan; Ukraine; Hungary; many regions in the U.S. (including Connecticut and Bergen Hill ); as well as in Bohemia and Moravia in the Czech Republic.

Crystal structure

Datolith crystallizes in the monoclinic space group P21 / c with lattice parameters a = 4.836 Å, b = 7.61 Å, c = 9.64 Å and β = 90.4 ° ​​, and four formula units per unit cell.