Rengeit

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Rengeit
General and classification
other names

IMA 1998-055

chemical formula Sr 4 Ti 4 ZrO 8 [Si 2 O 7 ] 2
Mineral class
(and possibly department) 		Silicates and germanates - group silicates (sorosilicates)
System no. to Strunz
and to Dana 		9.BE.70 ( 8th edition : VIII / C.17)
02.56.08.05
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / a (No. 14, position 3)Template: room group / 14.3
Lattice parameters a  = 13.9830  Å ; b  = 5.6722 Å; c  = 11.9960 Å
β  = 114.215 °
Formula units Z  = 2
Physical Properties
Mohs hardness 5 to 5.5
Density (g / cm 3 ) calculated: 4.12
Cleavage Please complete!
Break ; Tenacity brittle
colour dark brown
Line color light green brown
transparency transparent
shine Diamond luster
Crystal optics
Optical character biaxial positive
Pleochroism strong: light green to light green brown with less than 1% rare earths : light purple to greenish brown with about 3 to 10% rare earths

Rengeit is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the monoclinic crystal system with the chemical composition Sr 4 Ti 4 ZrO 8 [Si 2 O 7 ] 2 . By substitution , up to 10 percent by weight of light rare earths and small amounts of Ca , Al , Fe , Nb and Ba can be present.

Rengeit only develops small, dark brown crystals in granular aggregates with a diamond luster on the crystal surfaces. Rengeit is a polymorph of Strontiochevkinit and structurally the Perrierit similar.

Etymology and history

Rengeit was first discovered on the scree beach Oyashirazu near Itoigawa in Japan, more precisely in the jade stones found there .

The mineral was analyzed and described in 2001 by H. Miyajima, S. Matsubara, R. Miyawaki, K. Yokoyama and K. Hirokawa, who named it after the mountain Renge near the type locality Oyashirazu.

classification

In the outdated, but still in use 8th edition of the mineral systematics according to Strunz , the Rengeit belonged to the mineral class of "silicates and Germanates" and there to the department of " group silicates (sorosilicates)", where together with Chevkinit- (Ce) , Dingdaohengit- ( Ce) , Maoniupingit- (Ce) , Matsubarait , Perrierit- (Ce) , Perrierit- (La) , Polyakovit- (Ce) , Stavelotit- (La) and Strontiochevkinit the "Chevkinit-series" with the system number. VIII / C.17 formed.

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 assigns Rengeit to the class of “silicates and germanates” and there in the department of “group silicates (sorosilicates)”. However, this section is further subdivided according to the type of group formation, the possible presence of further anions and the coordination of the cations , so that the mineral according to its composition and structure in the sub-section “Si 2 O 7 groups with additional anions; Cations in octahedral [6] and greater coordination “can be found, where it is found together with chevkinite (Ce) , dingdaohengite (Ce) , carnasurtite (Ce) , maoniupingite (Ce) , matsubaraite , perrierite (Ce ), Perrierite (La) , polyakovite (Ce) and strontiochevkinite form the unnamed group 9.BE.70 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Rengeit to the class of "silicates and Germanates" and there in the department of "group silicates". Here he is together with chevkinite (Ce), strontiochevkinite, perrierite (Ce), orthochevkinite , matsubaraite , polyakovite (Ce), maoniupingite (Ce) and dingdaohengite (Ce) in the " perierite-chevkinite group " the system no. February 56, 2008 within the subsection “Group silicates: Si 2 O 7 groups and O, OH, F and H 2 O with cations in [4] and / or> [4] coordination”.

Crystal structure

Rengeit crystallizes monoclinically in the space group P 2 1 / a (space group no. 14, position 3) with the lattice parameters a  = 13.9830  Å ; b  = 5.6722 Å; c  = 11.9960 Å and β = 114.215 ° and 2 formula units per unit cell . Template: room group / 14.3

Education and Locations

At the type locality, Rengeit occurs in xenomorphic aggregates of up to 9 mm in size in jade . In addition to omphacite and jadeite , paragenesis also includes titanite , zirconium and tauconite . Rengeit is believed to have originated from the reaction of strontium-rich fluids with Zr and Ti minerals during high-grade metamorphosis .

In addition to its type locality Oyashirazu in Japan, Rengeit has so far (as of 2011) only been found on Kaskasnjuntschorr ( Каскаснюнчорр ) in the Chibinen on the Russian Kola Peninsula.

See also

literature

  • Hiroshi Miyajima, Satoshi Matsubara, Ritsuro Miyawaki, K. Yokoyama, K. Hirokawa: Rengeit, Sr 4 ZrTi 4 Si 4 O 22 , a new mineral, the Sr-Zr analogue of perrierite from the Itoigawa-Ohmi district, Niigata Prefecture, central Japan . In: Mineralogical Magazine , February 2001, Volume 65 (1), pp. 111–120 (English, PDF 650 kB )

Web links

Individual evidence

  1. ↑ Webmineral - Rengeite (English)
  2. ↑ a b c Ritsuro Miyawaki, Satoshi Matsubara, Hiroshi Miyajima: The crystal structure of rengeite, Sr 4 ZrTi 4 (Si 2 O 7 ) 2 O 8 . In: Journal of Mineralogical and Petrological Sciences . tape 97 , 2002, p. 7–12 ( rruff.info [PDF; 557 kB ; accessed on December 13, 2016]).
  3. ↑ Find location list for Rengeit in the Mineralienatlas and in Mindat