Wooldridgeit

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Wooldridgeit
General and classification
other names

IMA1997-037

chemical formula Na 2 CaCu 2+ 2 (P 2 O 7 ) 2 · 10H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.FC.25 ( 8th edition : 7 / C.35-20)
05/40/14/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol monoclinic; m
Space group Fdd 2 (No. 43)Template: room group / 43
Lattice parameters a  = 11.938 (1)  Å ; b  = 32.854 (2) Å; c  = 11.017 (1) Å
α  = 90 °; β  = 90 °; γ  = 90 °
Formula units Z  = 8
Physical Properties
Mohs hardness 2-3
Density (g / cm 3 ) 2.279 (calculated)
Cleavage no
Break ; Tenacity irregular
colour blue green
Line color very pale light blue
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.508 (1)
n β  = 1.511 (1)
n γ  = 1.517 (1)
Birefringence δ = 0.009
Optical character biaxial negative
Axis angle 2V = 76.2 (5) ° (measured); 71 (10) (calculated)
Pleochroism none

The mineral Wooldridgeit is a very rare, hydrous diphosphate with the chemical composition Na 2 CaCu 2+ 2 (P 2 O 7 ) 2 · 10H 2 O. It crystallizes with orthorhombic symmetry and forms blue-green, isometric crystals in the shape of compressed octahedra , the rarely larger than 1 mm.

Wooldridgeit is only known from a few localities worldwide. The type locality is the Judkins Quarry at Nuneaton in Warwickshire , England . Wooldridgeit is formed at very low temperatures and pressures when calcium- and copper-containing rocks come into contact with groundwater .

Etymology and history

In September 1999, RE Starkey and amateur mineralogist and gemologist James Wooldridge discovered tiny bluish crystals of an unknown mineral on samples from the three-year-old Judkins quarry near Nuneaton in Warwickshire, England. Wooldridge died in 1995 before the new mineral could be thoroughly examined. Neil Hubbard sent the samples to Frank Hawthorne at the University of Manitoba's Department of Geological Sciences at Winnipeg , Manitoba , Canada for structure determination , where they were extensively studied and identified as a new mineral. It was named after its discoverer James Wooldridge and was recognized as a new mineral in 1997 with the number IMA 1997-037 by the International Mineralogical Association (IMA).

Natural polyphosphates were unknown for a long time and it was assumed that they could not form under geologically relevant conditions until the first natural diphosphate was described in 1983 with canaphite .

Wooldridgeit is the second mineral with a pyrophosphate anion. Since then (March 2020) only 2 other polyphosphate minerals have been recognized by the IMA, the triphosphates Kanonerovite and Hylbrownit .

classification

Since Wooldridgeit was only recognized as an independent mineral in 1997, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . Only in the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , was the mineral given the system and mineral number. VII / C.35-20 . In the "Lapis system" this corresponds to the class of "phosphates, arsenates and vanadates" and there the section " Hydrous phosphates, without foreign anions ", where Wooldridgeit together with canaphite the group " Hydrous diphosphates [P 2 O 7 ] 4- "Forms (as of 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, assigns the Wooldridgeit to the division "Polyphosphates, Polyarsenates, [4] -Polyvanadates". This is further subdivided according to OH and H 2 O content, so that the mineral can be found in the sub-section “Diphosphates etc. with only H 2 O” according to its composition , where it is the only member of the unnamed group 8.FC. 25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Wooldridgeit to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates, etc.". Here he is to be found as the only member of the unnamed group 05/40/14 within the subdivision “Water-containing phosphates etc., with various formulas”.

Chemism

Wooldridgeit is a water-containing sodium - calcium - copper - diphosphate with the idealized composition Na 2 CaCu 2+ 2 (P 2 O 7 ) 2 · 10H 2 O. Little is known about possible substitutions due to the rarity of Wooldridgeit. The measured composition of Wooldridgeit from the type locality shows only low levels of potassium and magnesium :

  • (Na 1.96 K 0.03 ) Ca 1.00 (Cu 2+ 1.85 Mg 0.04 ) P 4.04 O 14 · 10H 2 O.

A nickel equivalent with the composition Na 2 CaNi 2+ 2 (P 2 O 7 ) 2 · 10H 2 O is known synthetically .

Crystal structure

Wooldridgeite structure CuP2O7H2O group
Wooldridgeit structure: chains of the CuP2O7H2O groups, view perpendicular to the b-axis

Wooldridgeit crystallizes with orthorhombic symmetry of the space group Fdd 2 (space group no. 43) and 8 formula units per unit cell . The natural Wooldridgeit from the type locality has the lattice parameters a  = 11.938 (1)  Å , b  = 32.854 (2) Å and c  = 11.017 (1) Å. Template: room group / 43

Phosphorus (P 5+ ) occupies two tetrahedral positions surrounded by 4 oxygen ions. The two tetrahedra are connected by a common oxygen ion at one corner to form a P 2 O 7 group.

Copper (Cu 2+ ) is surrounded by four oxygen and two water molecules in the form of an octahedron , which is distorted by the Jahn-Teller effect along an axis to form a square bipyramid . The four oxygens surround the Cu 2+ ion in the form of a square and form short bonds to the copper. The two water molecules are at a much greater distance at the tips of the bipyramid and only form very weak bonds to the copper. These copper bipyramids are linked by their syringes and the P 2 O 7 groups to form chains along [101].

Sodium (Na + ) is octahedral surrounded by two oxygen and four water molecules. These Na octahedra are connected by common corners to form chains along [101] that lie next to the Cu 2+ (P 2 O 7 ) (H 2 O) chains to which they are connected on one side.

Calcium (Ca 2+ ) is octahedral surrounded by four oxygen and two water molecules. The Ca octahedra lie between the Cu-P-Na bands and connect them in the direction of the b-axis.


Education and Locations

Wooldridgeit crystallizes at very low temperatures and pressures when calcium- and copper-containing rocks come into contact with groundwater .

In its type locality , the Judkins quarry near Nuneaton in Warwickshire , England , Wooldridgeit is found together with calcite , barite and copper sulphides, the weathering of which it formed.

So far only two other occurrences of Wooldridgeit have been documented, the Clara mine in Oberwolfach in the Black Forest , Baden-Württemberg and the Roughton Gill Mine near Caldbeck in the Allerdale district in Cumbria , England , where Wooldridgeit occurs together with chrysocolla in porous quartz aggregates .

See also

Web links

Individual evidence

  1. ↑ a b Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed March 8, 2020 .
  2. ↑ a b Wooldridgeite. In: mindat.org. Hudson Institute of Mineralogy, accessed March 10, 2020 .
  3. ↑ a b c Mineralienatlas: Wooldridgeit
  4. ↑ a b c Mark A. Cooper, Frank C. Hawthorne: The crystal structure of wooldridgeite, Na 2 CaCu 2+ 2 (P 2 O 7 ) 2 (H 2 O) 10 , a novel copper pyrophosphate mineral . In: The Canadian Mineralogist . tape 37 , 1999, pp. 73–81 ( rruff.info [PDF; 823 kB ; accessed on March 10, 2020]).
  5. ↑ a b c d e f g h i j k l m n o p q r s t u v w x FC Hawthorne, MA Cooper, DI Green, RE Starkey, AC Roberts, JD Grice: Wooldridgeite, Na 2 CaCu 2+ 2 (P 2 O 7 ) 2 (H 2 O) 10 : a new mineral from Judkins Quarry, Warwickshire, England . In: Mineralogical Magazine . tape 63 , 1999, pp. 13–16 ( rruff.info [PDF; 376 kB ; accessed on March 10, 2020]).
  6. ↑ a b List of localities for Wooldridgeit in the Mineralienatlas and Mindat
  7. ↑ K. Byrappa: The possible reasons for the absence of condensed phosphates in nature . In: Physics and Chemistry of Minerals . tape 10 , 1983, p. 94-95 , doi : 10.1007 / BF00309591 .
  8. ^ A b Roland C. Rouse, Donald R. Peacor, Robert L. Freed: Pyrophosphate groups in the structure of canaphite, CaNa 2 P 2 O 7 · 4H 2 O: The first occurrence of a condensed phosphate as a mineral . In: American Mineralogist . tape 73 , 1988, pp. 168–171 ( rruff.info [PDF; 448 kB ; accessed on February 10, 2020]).
  9. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  10. ↑ Yun-Cheng Cui and Yan-Hui Zhaoa: Disodium calcium dinickel (II) to [diphosphate (V)] decahydrate . In: Acta Crystallographica Section E . tape 67 , 2011, p. i13-i14 , doi : 10.1107 / S160053681100016X .
  11. ↑ Trevor F. Bridges, David I. Green, Michael S. Rumsey, C. Michael Leppington: A review of the mineralization of the Roughton Gill Mines, Caldbeck Fells, Cumbria: Part 3 Roughton Gill Mine . In: Journal of the Russell Society . tape 14 , 2011, p. 3–23 ( researchgate.net [PDF; 11.1 MB ; accessed on March 10, 2020]).