Titanite

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Titanite
Titanite crystals on Amphibole - Ochtendung, Eifel, Germany.jpg
Several reddish brown titanite crystals on an amphibole (image size 2 mm)
General and classification
chemical formula CaTi [O | SiO 4 ]
Mineral class
(and possibly department) 		Silicates and germanates - island silicates (nesosilicates)
System no. to Strunz
and to Dana 		9.AG.15 ( 8th edition : VIII / B.12)
April 52nd, 03.01
Similar minerals Cassiterite , rutile
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / c (No. 15)Template: room group / 15
Lattice parameters a  = 6.57  Å ; b  = 8.72 Å; c  = 7.44 Å
β  = 119.7 °
Formula units Z  = 4
Frequent crystal faces {111}, {110}, {102}, {100}, {001}, {11 2 }
Twinning often after {100}, contact and penetration twins; less often lamellar after {221}
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) measured: 3.48 to 3.60; calculated: [3.53]
Cleavage clearly according to (110), indistinctly according to (111)
Break ; Tenacity mussely; brittle
colour colorless, black, brown, gray, green, yellow, red
Line color White
transparency transparent to opaque
shine Diamond luster, glass luster; Resin gloss
radioactivity weakly radioactive
Crystal optics
Refractive indices n α  = 1.843 to 1.950
n β  = 1.870 to 2.034
n γ  = 1.943 to 2.110
Birefringence δ = 0.100 to 0.160
Optical character biaxial positive
Axis angle 2V = 17 ° to 40 °
Pleochroism Visible: X – Y – Z = colorless - yellow to green - red to yellow-orange
Other properties
Chemical behavior soluble in concentrated sulfuric acid

Titanite , also called Sphen , is a frequently occurring mineral from the mineral class of "silicates and germanates" with the chemical formula CaTi [O | SiO 4 ] and is therefore chemically a calcium - titanium - silicate . Structurally, titanite is one of the island silicates .

Titanite crystallizes in the monoclinic crystal system and develops mostly tabular or wedge-shaped pointed crystals and twins with a glass-like to diamond-like sheen on the surfaces. But it also occurs in the form of granular to massive mineral aggregates . In its pure form, Titanite is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also appear translucent white and, due to foreign admixtures, take on a green, yellow, red, gray or brown to black color.

Etymology and history

Titanite was first found in 1795 in the Hauzenberg graphite mines in the Bavarian Forest and described by Martin Heinrich Klaproth , who named the mineral after its titanium content.

The synonym Sphen ( give a wiki. Σφήν Sphen "wedge") received Titanit due to its often wedge-shaped crystal forms.

classification

Already in the outdated, but partly still in use systematics of minerals according to Strunz (8th edition) , titanite belonged to the mineral class of "silicates and Germans" and there to the department of "island silicates with non-tetrahedral anions (Neso subsilicates)", where it was classified as Namesake of the "Titanit series" with the system no. VIII / B.12 and the other members malayaite , trimounsite (Y) and vanadomalayaite .

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also classifies titanite in the category of "island silicates". However, this is more precisely subdivided according to the possible presence of additional anions and the coordination of the cations involved , so that the mineral is classified in the sub-section “Island silicates with additional anions; Cations in mostly [6] and> [6] coordination "can be found, where only together with malayaite and vanadomalayaite the" titanite group "with the system no. 9.AG.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns titanite to the class of "silicates and Germans" and there to the department of "island silicates: SiO 4 groups and O, OH, F and H 2 O". Here it is also together with malayaite and vanadomalayaite in the " titanite group " with the system no. April 52, 2003 within the subdivision “ Island silicates: SiO 4 groups and O, OH, F and H 2 O with cations in [6] and / or> [6] coordination”.

Crystal structure

Titanite crystallizes monoclinically in the space group C 2 / c (space group no. 15) with the lattice parameters a  = 6.57  Å ; b  = 8.72 Å; c  = 7.44 Å and β = 119.7 ° as well as 4 formula units per unit cell . Template: room group / 15

properties

Chemical properties

The mineral is sensitive to acids (complete solubility in sulfuric acid ), alkalis and the effects of heat.

Physical Properties

In front of the soldering tube , titanite melts at the edges to form dark glass.

Depending on where it was found, the mineral can be weakly radioactive due to the addition of uranium , thorium or radium and have a specific activity of around 82  Bq / g (for comparison: natural potassium 31.2 Bq / g).

Education and Locations

Crystal specimen with greenish titanites from the Tormiq Valley, Haramosh Mountains, Pakistan
Large titanite crystals (black) next to diopside (dark green) and quartz (white) in a pegmatite (Radium Creek, South Australia)
yellowish titanite from Ochtendung in the Eifel

Titanite has a relatively wide stability range, that is, it can form at pressures of up to 1.4 Gpa and temperatures of up to 700 ° C (according to WG Ernst and Jun Liu 1996) and accordingly arise either directly through igneous or indirectly through metamorphic processes in pegmatites .

As a frequent mineral formation, Titanite can be found at many sites, with over 4500 sites being known to date (as of 2016).

Attractive, collectible titanites with crystals up to 18 cm in size were found on alpinotype corridors in Austria ( Zillertal , Felbertal ), Switzerland ( Tujetsch , Binntal ) and in Russia (Dodo Mine, northern Urals ). Large but imperfect crystals weighing up to 40 kg have been discovered in Canada (Ontario) and the United States (New York). Another famous historical find in Germany is the Plauensche Grund between Dresden and Freital . In forthcoming there monzonite the famous Titanitspiegel were found.

Rich deposits with three or more localities are in Argentina , Australia , Bolivia , Brazil , Bulgaria , Chile , China , Germany , Finland , France , Greece , India , Ireland , Italy , Japan , Cameroon , Canada , Kazakhstan , Kyrgyzstan , on Cuba , on Madagascar , Malawi , Morocco , Mexico , Mongolia , Namibia , North Korea , Norway , Austria , Pakistan , Portugal , Romania , Russia , Sweden , Switzerland , Slovakia , Spain , Sri Lanka , South Africa , South Korea , Tanzania , the Czech Republic , the Ukraine , Hungary , the United Kingdom (Great Britain) and the United States of America (USA).

use

several titanites in triangular facet cut

raw material

Titanite is used locally as a raw material for the production of titanium dioxide (TiO 2 ). The naturally occurring titanium dioxides rutile , anatase and brookite are preferred, however .

Gemstone

Clear varieties are processed into gemstones and, in the facet cut , serve primarily as a substitute for diamonds . However, due to its sensitivity to acids, alkalis and the effects of heat, the mineral is not easy to process.

See also

literature

  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 681–682 (first edition: 1891).
  • Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags GmbH, Munich et al. 2002, ISBN 3-405-16332-3 , p. 210 .

Web links

Commons : Titanite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  553 .
  2. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th, revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  472 .
  3. ↑ a b Webmineral - Titanite
  4. ^ A b c d Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin / New York 1981, ISBN 3-11-006823-0 .
  5. ↑ a b c Titanite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF 76.5 kB).
  6. ↑ a b c d e f Mindat - Titanite
  7. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  682 (first edition: 1891).
  8. ^ Science online - radioactive age determination
  9. ↑ Heinrich Mache: About the emergence of radioactive sources. In: Communications of the Alpine Geological Association. Volume 34, 1941, p. 75 ( uibk.ac.at PDF 363 kB; p. 7)
  10. ^ WG Ernst, Jun Liu: Experimental phase-equilibrium study of Al and Ti contents of calcic amphibole in MORB — A semiquantitative thermobarometer. In: American Mineralogist. Volume 83, 1998, pp. 952–969 ( minsocam.org PDF 176.4 kB)
  11. ↑ Mindat - Number of locations for Titanite
  12. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 206-207 .
  13. ↑ Find location list for Titanit in the Mineralienatlas and Mindat
  14. ^ Precious stone etiquette by Prof. Leopold Rössler - Titanit
  15. ↑ realgems.org - Titanite (with many examples of cut Titanite)