Helmutwinklerite

Helmutwinklerite
Yellowish Helmutwinklerite crystals with fines from Vouves, Thasos Island , Macedonia Department, Greece
General and classification
other names	IMA 1979-010
chemical formula	PbZn 2 (AsO 4 ) 2 · 2H 2 O PbZn 2 [AsO 4 ] 2 • 2H 2 O
Mineral class (and possibly department)	Phosphates, arsenates and vanadates
System no. to Strunz and to Dana	8.CG.20 02/40/09/02
Crystallographic Data
Crystal system	triclinic
Crystal class ; symbol	triclinic pinacoidal; 1
Space group	P 1 (No. 2)
Lattice parameters	a  = 5.606  Å ; b  = 5.610 Å; c  = 7.617 Å, α  = 70.19 °; β  = 69.91 °; γ  = 69.18 °
Formula units	Z  = 1
Frequent crystal faces	{001}, {100}, {010}, {011}, {101}, {111}, {112}
Physical Properties
Mohs hardness	4.5, VHN 25  = 350 kg / mm 2
Density (g / cm 3 )	5.3 (measured); 5.21 to 5.29 (calculated)
Cleavage	no
Break ; Tenacity	clamshell; not specified
colour	colorless to light blue, sea green
Line color	White
transparency	translucent to translucent
shine	Glass gloss on crystal surfaces, resin gloss on fractured surfaces
Crystal optics
Refractive indices	n α  = 1.72, 1.83 n β  = 1.80, 1.87 n γ  = 1.98, 1.98
Refractive index	n  = 1.849 (calculated, Gladstone-Dale)
Birefringence	δ = 0.26; 0.150
Optical character	biaxial positive
Axis angle	2V = 73 ° (calculated), 70 ° (measured)
Pleochroism	none
Other properties
Chemical behavior	Completely soluble in hydrochloric acid, less readily soluble in nitric acid and sulfuric acid

Helmutwinklerite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the triclinic crystal system with the chemical composition PbZn ₂ [AsO ₄ ] ₂ · 2H ₂ O and is therefore chemically a water-containing lead - zinc - arsenate .

After the pinacoid {001}, helmutwinklerite develops tabular crystals up to a maximum of 5 mm in size, which can be colorless to slightly light blue or sea green in color.

Etymology and history

The discoverers of the Helmutwinklerite are Ltd. BR Woolfe, General Manager , and RA Schedler, Senior Mineralogist at Tsumeb Mining Corporation, who noticed the white to light blue crystals on a step found in the Tsumeb Mine and who made this step available to the authors of the 1979 type publication for identification. Corresponding investigations led to the determination of the presence of a new mineral, which was recognized by the International Mineralogical Association (IMA) in 1979 and described as helmutwinklerite by the two German researchers at the University of Göttingen Peter Süsse and Günther Schnorrer in 1980 . The mineral was named after the German mineralogist Helmut Gustav Franz Winkler (1915–1980) in recognition of his contributions to petrology, mineralogy and crystallography. Winkler is one of the founders of experimental petrology in Germany and is the author of a standard work on the petrology of metamorphic rocks.

Type material of the mineral is kept at the Geoscientific Center in the Georg-August-Universität Göttingen (holotype, collection no. 7.4.127.1).

classification

The current classification of the International Mineralogical Association (IMA) counts the helmutwinklerite to the tsumcorite group with the general formula Me (1) Me (2) ₂ (XO ₄ ) ₂ (OH, H ₂ O) ₂ , in which Me (1), Me (2) and X different positions in the structure of the minerals of the tsumcorite group with Me (1) = Pb ²⁺ , Ca ²⁺ , Na ⁺ , K ⁺ and Bi ³⁺ ; Me (2) = Fe ³⁺ , Mn ³⁺ , Cu ²⁺ , Zn ²⁺ , Co ²⁺ , Ni ²⁺ , Mg ²⁺ and Al ³⁺ and X = As ⁵⁺ , P ⁵⁺ , V ⁵⁺ and represent S ⁶⁺ . To Tsumcoritgruppe include not only Helmutwinklerit still Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite .

Since the Helmutwinklerite was only recognized as an independent mineral in 1979, 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.31-100 . In the "Lapis Classification" corresponds to the class of "phosphates, arsenates and vanadates" and then the department "water containing phosphates, without foreign anions " where Helmutwinklerit with Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Mounanait , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinkgartrellit the "Tsumcorit / Gartrellit group" formed (as 2018).

The 9th edition of Strunz's mineral systematics , which has been valid since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns helmutwinklerite to the category of “phosphates etc. without additional anions; with H ₂ O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral is classified in the sub-section “With large and medium-sized cations; RO ₄  : H ₂ O = 1: 1 ”is to be found where the“ Helmutwinkleritgruppe ”with the system no. 8.CG.20 and the other members gartrellite, lukrahnite, phosphogartrellite, rappoldite and zinc gartrellite.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns helmutwinklerite to the class of "phosphates, arsenates and vanadates" and there in the department of "water-containing phosphates, etc.". Here he is the namesake of the " Helmutwinklerite subgroup " with the system no. 02/40/09 and the other members cobalt sumcorite, mawbyite , nickel schneebergite , rappoldite, snow mountainite, Thometzekit and tsumcorite within the subsection "water-containing phosphates etc., with A ²⁺ (B ²⁺ ) ₂ (XO ₄ ) × x (H ₂ O) " to find.

Chemism

Helmutwinklerite has the measured composition Pb _0.90 (Zn _2.17 Cu _0.12 ) _{Σ = 2.29} (As _0.96 O ₄ ) ₂ · 2.19H ₂ O, which is simplified as PbZn ₂ (AsO ₄ ) ₂ · 2H ₂ O can be written and requires 24.97% ZnO, 34.24% PbO, 35.26% As ₂ O _5, and 5.53% H ₂ O

Helmutwinklerite is a Pb-Zn-dominant representative of the tsumcorite group. B. the zinc-dominant analogue to cobalt-dominated rappoldite. In addition, the compound PbZn ₂ (AsO ₄ ) ₂ · 2H ₂ O is dimorphic and occurs naturally as a monoclinic crystallizing tsumcorite in addition to the triclinically crystallizing helmutwinklerite . However, the chemical formula for tsumcorite is also given as PbZnFe [(H ₂ O, OH) | AsO ₄ ] ₂ , which means that, strictly speaking, there would no longer be any dimorphism.

Crystal structure

Helmutwinklerite crystallizes in the triclinic crystal system in the space group P 1 (space group no. 2) with the lattice parameters a  = 5.606  Å ; b  = 5.610 Å; c  = 7.617 Å; α = 70.19 °; β = 69.91 ° ​​and γ = 69.18 ° and one formula unit per unit cell .

The crystal structure of the Helmutwinklerite corresponds to the general structure of the representatives of the Helmutwinklerite group. Chains of parallel [010] arranged Zn (O, OH) ₆ - octahedra are connected to one another by corner - linked AsO ₄ - tetrahedra in such a way that layers parallel (001) are formed. These layers are in turn linked to one another by Pb ^[8] atoms and hydrogen bonds .

properties

morphology

Drawing of a helmutwinklerite crystal from the Tsumeb mine

According to {001}, helmutwinklerite forms tabular crystals up to a maximum of 5 mm in size, on which in addition to the supporting form, the pinacoid {001}, the pinacoids {100}, {010}, {011}, {101}, {111} and {112} have been identified. The original indexing was based on {100} tabular crystals with {001}, {010}, {1 1 0} and {11 1 }, but has turned out to be incorrect.

physical and chemical properties

The crystals of Helmutwinklerite are colorless, light blue or sea green, their line color is indicated as white. The surfaces of the translucent to transparent crystals have a glass-like sheen , whereas the fracture surfaces are glossy with resin.

The mineral has no cleavability , breaks but similar glass or quartz , wherein the fractured surfaces are formed conchoidal. With a Mohs hardness of 4.5, helmutwinklerite is one of the medium-hard minerals that are somewhat easier to scratch with a pocket knife than the reference mineral apatite . The measured density of the mineral is 5.3 g / cm³, its calculated density is between 5.21 and 5.29 g / cm³.

Helmutwinklerite is completely soluble in hydrochloric acid , but less soluble in nitric acid and sulfuric acid.

Education and Locations

As a very rare mineral formation, Helmutwinklerite could so far (as of 2016) only be described from one other site in addition to its type locality . The type locality is the world-famous Cu-Pb-Zn-Ag-Ge-Cd deposit of the "Tsumeb Mine" (Tsumcorp Mine) in Tsumeb , Oshikoto region , Namibia , where helmutwinklerite was first observed in a solution cavity in the tennantite and here by quartz and Willemit was accompanied. Another cavity on the same step contained koritnigit , warikahnit and cuproadamin .

For a few more steps with helmutwinklerite, the E9 pillar on the 31st level is known to be the exact location in the Tsumeb mine. Here, too, the mineral is associated with white coritnigite, willemite, pale yellow warikahnite, cuproadamine and quartz. Helmutwinklerite was the first to be formed from these minerals and is therefore the oldest mineral in the succession . Helmutwinklerite is a typical secondary mineral and formed in the second (lower) oxidation zone of the hydrothermal polymetallic ore deposit Tsumeb, which is located in dolomite stones , from lead and zinc-containing sulfides (galena, sphalerite), the arsenic originating from the decomposition of the arsenic pale ore tennantite. Tennantite probably also supplied the small amounts of copper that can be detected in the analyzes of the Helmutwinklerite.

The only other location besides the type locality, which only provided one stage, is the “Shaft No. 132 "of the" Christiana Mine "near Agios Konstantinos (Kamariza) near Plaka, Lavrion District, Attica Region , Greece . Helmutwinklerite forms colorless to pale green crusts from morphologically only indistinctly developed crystals. Helmutwinklerite crystals with copper content are clearly green in color, while low-copper to copper-free crystals are colorless. The matrix consists of a mixture of quartz and decomposed tennantite, which - as in the Tsumeb mine - is likely to be responsible for both the arsenic and the copper. The paragenesis with warikahnite, koritnigit, adamin and tsumcorite is similar to that in the Tsumeb mine.

use

Due to its rarity, helmutwinklerite is only of interest to mineral collectors.

See also

• List of minerals

literature

• Michael Fleischer , Louis J. Cabro, George Y. Chao, Adolf Pabst : New Mineral Names . In: American Mineralogist . tape 65 , 1998, pp. 1067 (English, minsocam.org [PDF; 721 kB ; accessed on June 29, 2019]).
• John Leslie Jambor , Edward S. Grew, Andrew C. Roberts: New Mineral Names . In: American Mineralogist . tape 83 , 1998, pp. 896 (English, rruff.info [PDF; 94 kB ; accessed on June 29, 2019]).
• Peter Süsse, Günther Schnorrer: Helmutwinklerite, a new arsenate mineral from Tsumeb, SW Africa . In: New Yearbook Mineralogy, monthly books . tape 1980 , no. 3 , 1980, p. 118-124 (English).
• Helmutwinklerite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 69 kB ; accessed on June 29, 2019]).

Web links

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

• Mineral Atlas: Helmutwinklerite (Wiki)
• Helmutwinklerite. In: mindat.org. Hudson Institute of Mineralogy, accessed June 30, 2019 . 
• David Barthelmy: Helmutwinklerite Mineral Data. In: webmineral.com. Retrieved June 30, 2019 . 
• American-Mineralogist-Crystal-Structure-Database - Helmutwinklerite. In: rruff.geo.arizona.edu. Retrieved June 30, 2019 . 

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n o p q r s t u v w} Peter Süsse, Günther Schnorrer: Helmutwinklerite, a new arsenate mineral from Tsumeb, SW Africa . In: New Yearbook Mineralogy, monthly books . tape 1980 , no. 3 , 1980, p. 118-124 (English).
2. ↑ ^{a b c d e f g h i j k l} Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , no. 2 , 1998, p. 179–206 , doi : 10.1127 / ejm / 10/2/0179 (English).
3. ↑ ^{a b c d e f} Helmutwinklerite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 69  kB ; accessed on June 29, 2019]).
4. ↑ ^{a b c d e f} 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.  484 (English).
5. ↑ ^{a b c d} Paul Keller , Wolfgang Bartelke: TSUMEB! new minerals and their associations . In: Mineralogical Record . tape  13 , no. 3 , 1982, pp. 137-148 (English).
6. ↑ Type mineral catalog Germany - Helmutwinklerite. In: typmineral.uni-hamburg.de. Mineralogical Museum of the University of Hamburg, December 8, 2017, accessed on June 30, 2019 .  
7. ↑ 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 .
8. ↑ 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 21, 2020 .  
9. ↑ Paul Keller : Tsumeb / Namibia - one of the most spectacular mineral discovery sites on earth . In: Lapis . tape  9 , no. 7/8 , 1977, pp. 13-63 .
10. ↑ Localities for Helmutwinklerite. In: mindat.org. Hudson Institute of Mineralogy, accessed June 30, 2019 .  
11. ↑ List of locations for helmutwinklerite from the Mineralienatlas and Mindat , accessed on March 21, 2020.
12. ↑ Branko Rieck: Rare arsenates from the Kamariza and other new finds from Lavrion . In: Lapis . tape 24 , no. 7/8 , 1999, p. 68-76 .