Carmel gray

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Carmel gray
Scanning electron microscope image of carmeltazite 01.png
Electron microscope picture of carmeltacite in corundum
General and classification
other names
  • IMA 2018-103
  • Carmel gray
chemical formula ZrAl 2 Ti 4 O 11
Mineral class
(and possibly department) 		Oxides and hydroxides
Crystallographic Data
Crystal system Orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m  2 / m  2 / m
Space group Pnma (No. 62)Template: room group / 62
Lattice parameters a  = 14.0951 (9)  Å ; b  = 5.8123 (4) Å; c  = 10.0848 (7) Å
Formula units Z  = 4
Physical Properties
Mohs hardness not defined
Density (g / cm 3 ) calculated: 4.122
Cleavage not defined
colour black
Line color reddish brown
transparency not defined
shine Metallic luster
Crystal optics
Birefringence δ = weak to moderate in reflected light
Pleochroism weak: dark brown to dark green

Carmeltacite also Carmeltacite is a very rarely occurring mineral with the chemical composition ZrAl 2 Ti 4 O 11 and thus chemically a zirconium - aluminum - titanium - oxide .

Carmeltacite crystallizes in the orthorhombic crystal system , but has so far only been found in the form of microscopic black crystals about 80  μm in size enclosed in corundum .

Etymology and history

Carmeltazite was discovered for the first time by geologists from Shefa Yamin during geological excavations in the deposits of the Kishon River near Haifa in the Carmel and Carmel Mountains in Israel . Analysis and first description was by William L. Griffin, Sarah EM Gain, Luca Bindi, Vered Toledo, Fernando Cámara, Martin Saunders and Suzanne Y. O'Reilly that the mineral after its type locality and the main constituents T itan, A luminium and Z irconium named. The test results and the chosen name were submitted to the International Mineralogical Association (IMA) for examination in 2018 (internal entry number of the IMA: 2018-103), which recognized the mineral as an independent mineral type in the same year.

The type of material (holotype) of the mineral is in the mineralogical collection of the Museo di Storia Naturale ( Natural History Museum ) in Florence under catalog number 3293 / I kept.

classification

Carmeltazite was only recognized as an independent mineral by the IMA in 2018 and published in 2019. An exact group assignment in the 9th edition of the Strunz'schen mineral systematics , the last update of which was carried out with the publication of the IMA list of mineral names in 2009, is therefore not yet known.

Due to its chemical composition, however, it can be assumed that carmeltacite is classified in the mineral class of "oxides and hydroxides".

Chemism

Eight microprobe analyzes on the type material from Carmeltazit resulted in an average composition of 1.5% SiO 2 , 24.9% ZrO 2 , 0.53% HfO 2 , 0.16% UO 2 , 0.06% ThO 2 , 18.8% Al 2 O 3 , 0.02% Cr 2 O 3 , 50.6% Ti 2 O 3 , 0.76% Sc 2 O 3 , 0.39% Y 2 O 3 , 1.89% MgO and 0.51 % CaO (all data in% by weight).

On the basis of 11 oxygen atoms, the empirical formula is calculated (Ti 3+ 3.60 Al 1.89 Zr 1.04 Mg 0.24 Si 0.13 Sc 0.06 Ca 0.05 Y 0.02 Hf 0.01 ) Σ = 7.04 O 11 , which has been idealized to ZrAl 2 Ti 4 O 11 . The idealized, theoretical composition of Carmeltacite thus consists of 24.03% by weight ZrO 2 , 19.88% by weight Al 2 O 3 and 56.09% by weight Ti 2 O 3 .

Crystal structure

Crystal structure of the Carmeltacite

Carmeltacite crystallizes orthorhombically in the space group Pmna (space group no. 53) with the lattice parameters a  = 14.0951 (9)  Å , b  = 5.8123 (4) Å and c  = 10.0848 (7) Å as well as four formula units per Unit cell . The crystal structure corresponds to a disturbed spinel structure. Template: room group / 53

Education and Locations

Carmeltazit formed as Phenocrysts (Xenokristalle) in the pockets of entrapped in Schmelzinterstitial corundum from the Cretaceous Carmel volcanoes Northern Israel. In addition to corundum, tistarite , anorthite , osbornite and unnamed rare earth phases in Ca-Mg-Al-Si-O-glass were found as accompanying minerals .

Apart from the Carmel Mountains, no other sites for Carmeltacite are known.

The mineral was formed during volcanic eruptions in the Cretaceous period, presumably at a depth of around 30 km (18 miles) from the boundary between the earth's crust and mantle .

use

The very rare mineral is marketed by the Shefa Yamin company with the protected name Carmel sapphire . The smaller finds are often embedded in sapphire, the largest piece found so far has 33.3 carats .

Contrary to what some media claim, however, Carmeltazite is no harder than a diamond . The theoretical density (calculated from the crystal structure) is 4.12 g / cm 3 and is higher than that of diamonds with 3.52 g / cm 3 . However, this does not lead to a higher hardness , which has not yet been defined for the Carmeltacite.

See also

literature

  • William L. Griffin, Sarah EM Gain, Luca Bindi, Vered Toledo, Fernando Cámara, Martin Saunders, Suzanne Y. O'Reilly: Carmeltazite, ZrAl 2 Ti 4 O 11 , a New Mineral Trapped in Corundum from Volcanic Rocks of Mt Carmel, Northern Israel . In: Minerals . tape 8 , no. 601 , 2018, p. 1–11 , doi : 10.3390 / min8120601 (English, available online at rruff.info [PDF; 3.9 MB ; accessed on February 21, 2019]).

Web links

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

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o p William L. Griffin, Sarah EM Gain, Luca Bindi, Vered Toledo, Fernando Cámara, Martin Saunders, Suzanne Y. O'Reilly: Carmeltazite, ZrAl 2 Ti 4 O 11 , a New Mineral Trapped in Corundum from Volcanic Rocks of Mt Carmel, Northern Israel . In: Minerals . tape 8 , no. 601 , 2018, p. 1–11 , doi : 10.3390 / min8120601 (English, available online at rruff.info [PDF; 3.9 MB ; accessed on February 25, 2019]).
  2. ↑ Mineral Atlas: Carmeltacite (Carmeltacite)
  3. ↑ IMA / CNMNC List of Mineral Names September 2009 (PDF 1.8 MB with the last official Strunz classification)
  4. ↑ Find location list for Carmeltacite in the Mineralienatlas and in Mindat
  5. Jump up ↑ William L. Griffin, Jin-Xiang Huang, Emilie Thomassot, Sarah EM Gain, Vered Toledo, Suzanne Y. O'Reilly: Super-reducing conditions in ancient and modern volcanic systems: sources and behavior of carbon-rich fluids in the lithospheric mantle . In: Mineralogy and Petrology . tape 112 , 2018, p. 101–114 , doi : 10.1007 / s00710-018-0575-x (English, available online at irp-cdn.multiscreensite.com [PDF; 3.4 MB ; accessed on February 25, 2019]).
  6. ↑ a b David Bressan: Carmeltazite: A New Unique Gemstone From Israel. In: forbes.com. Forbes, accessed February 25, 2019 .
  7. ↑ Leah Silverman: Extraterrestrial Mineral Harder Than Diamond Discovered In Israel. In: allthatsinteresting.com. January 11, 2019, accessed February 25, 2019 .