Woodwardite

from Wikipedia, the free encyclopedia
Woodwardite
Woodwardite-237529.jpg
Woodwardite (size: 2.9 × 1.8 × 0.7 cm) from Cornwall, England
General and classification
chemical formula ~ [(Cu, Al) 9 (OH) 18 ] [(SO 4 ) 2 · nH 2 O]
Mineral class
(and possibly department) 		Sulphates, selenates, tellurates, chromates, molybdates, tungstates
System no. to Strunz
and to Dana 		7.DD.35 ( 8th edition : VI / D.08)
31.02.02.01
Crystallographic Data
Crystal system trigonal (pseudohexagonal)
Crystal class ; symbol ditrigonal-scalenohedral; 3 2 / m
Space group R 3 m
Lattice parameters a  = 3.06  Å ; c  = 25.3 Å
Formula units Z  = 1/3
Physical Properties
Mohs hardness 2
Density (g / cm 3 ) 2.38
Cleavage Please complete!
colour greenish blue, turquoise blue
Line color pale blue
transparency transparent to translucent
shine Please complete!
Crystal optics
Refractive indices n α  = 1.552 to 1.571
n β  = 1.555 to 1.574
n γ  = 1.565 to 1.576
Birefringence δ = 0.013
Optical character biaxial positive

Woodwardite is a rarely occurring mineral from the mineral class of " sulfates , selenates , tellurates , chromates , molybdates and tungstates ". It crystallizes in the trigonal crystal system with the chemical composition Cu 1-x Al x (OH) 2 (SO 4 ) x / 2  • nH 2 O, x = 0.32 to 0.5 ( copper analogue of Zincowoodwardit ) or ~ [(Cu, Al) 9 (OH) 18 ] [(SO 4 ) 2 · nH 2 O] and develops fibrous or grape-like mineral aggregates of greenish-blue to turquoise-blue color and pale blue streak color .


Etymology and history

Woodwardite was first found in Cornwall (England) in 1866 and described by AH Church , who named the mineral after Samuel Pickworth Woodward (1821-1865), an English geologist and naturalist.

classification

In the now outdated 8th edition of the systematics of minerals according to Strunz , woodwardite belongs to the division of " water-containing sulfates with foreign anions ".

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001, divides this section more precisely according to the size of the cations involved and the crystal structure, so that Woodwardite is now in the sub-section of “With only medium-sized cations; Layers of edge-linked octahedra ”. Here he, together with Carrboydit , Glaukokerinit , Honessit , Hydrohonessit , Hydrowoodwardit , Motukoreait , Mountkeithit , Natroglaukokerinit , Nikischerit , Shigait , SO4 hydrotalcite 8.8A , SO4 hydrotalcite-11A wermlandite , Zinkaluminit and Zincowoodwardit the unnamed group 7.DD.35 .

The systematics of minerals according to Dana also assigns the mineral to the class of sulphates, but there in the division of "water-containing sulphates with hydroxyl or halogen". Here it is together with hydrowoodwardite , zincowoodwardite or the polytypes zincowoodwardite-1T and zincowoodwardite-3R in the woodwardite group with system no. 02/31/02 within the sub-section of "Water-containing sulphates with hydroxyl or halogen and the general formula (A + B 2+ ) 6 (XO 4 ) Z q × x (H 2 O)".

Education and Locations

Woodwardite forms as rare secondary mineral in the oxidation zone of copper - deposits .

Woodwardite has so far (as of 2010) been found at around 50 sites worldwide, including in Australia , Germany , France , Greece , Italy , Japan , Austria , Zambia , the United Kingdom (Great Britain) and the United States of America ( UNITED STATES).

Crystal structure

Woodwardite crystallizes trigonal in the space group R 3 m with the lattice parameters a  = 3.06  Å and c  = 25.3 Å as well as 1/3 formula units per unit cell .

See also

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 403 .
  2. ↑ a b Woodwardite at mindat.org (engl.)
  3. ↑ AH Church: IV.-A New Hydrated Cupric-aluminum Sulphate (English, PDF 309 kB)
  4. ↑ Mindat - Localities for Woodwardite

Web links

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