Tsumcorite

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title: "Tsumcorite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["arsenate-minerals", "lead-minerals", "zinc-minerals", "iron(ii)-minerals", "monoclinic-minerals", "minerals-in-space-group-12", "minerals-described-in-1971"] description: "Rare hydrated lead arsenate mineral" topic_path: "general/arsenate-minerals" source: "https://en.wikipedia.org/wiki/Tsumcorite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Rare hydrated lead arsenate mineral ::

::data[format=table title="Infobox mineral"]

Field	Value
name	Tsumcorite
category	Arsenate minerals
image	Tsumcorite-160209.jpg
caption	Tsumcorite from the Tsumeb Mine, Namibia
formula	PbZnFe2+(AsO4)2.H2O
IMAsymbol	Tmc
molweight	624.29 g/mol
strunz	8.CG.15
dana	40.02.09.01
system	Monoclinic
class	Prismatic (2/m)
(same H-M symbol)
symmetry	C2/m (no. 12)
unit cell	a = 9.124 Å, b = 6.329 Å
c = 7.577 Å; β = 115.3°; Z = 2
color	Yellow-brown, red-brown, orange
habit	Radiating, fibrous crusts
twinning	Common, on an unknown law
cleavage	Good on {001}
mohs
luster	Vitreous
refractive	nα = 1.87–1.91 nβ = 1.89–1.93 nγ = 1.92–1.96
opticalprop	Biaxial
pleochroism	Weak, yellow to yellow-green
2V	67–83.5°
streak	Yellow
gravity	5.2
solubility	Dissolves in HCl
diaphaneity	Translucent
references
::

| name = Tsumcorite | category = Arsenate minerals | boxwidth = | boxbgcolor = | image = Tsumcorite-160209.jpg | caption = Tsumcorite from the Tsumeb Mine, Namibia | formula = PbZnFe2+(AsO4)2.H2O | IMAsymbol = Tmc | molweight = 624.29 g/mol | strunz = 8.CG.15 | dana = 40.02.09.01 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m (no. 12) | unit cell = a = 9.124 Å, b = 6.329 Å c = 7.577 Å; β = 115.3°; Z = 2 | color = Yellow-brown, red-brown, orange | habit = Radiating, fibrous crusts | twinning = Common, on an unknown law | cleavage = Good on {001} | fracture = | tenacity = | mohs = | luster = Vitreous | refractive = nα = 1.87–1.91 nβ = 1.89–1.93 nγ = 1.92–1.96 | opticalprop = Biaxial | birefringence = | pleochroism = Weak, yellow to yellow-green | 2V = 67–83.5° | streak = Yellow | gravity = 5.2 | melt = | fusibility = | diagnostic = | solubility = Dissolves in HCl | diaphaneity = Translucent | other = | references = }} Tsumcorite is a rare hydrated lead arsenate mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb, in Namibia, in recognition of the Corporation's support for mineralogical investigations of the orebody at its Mineral Research Laboratory.

Unit cell

Tsumcorite belongs to the monoclinic crystal class 2/m, which means that it has a twofold axis of symmetry along the b axis and a mirror plane perpendicular to this, in the plane containing the a and c axes. The a and c axes are inclined to each other at angle β = 115.3°. The unit cell parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å. The structure is related to the brackebushite group structure.

Mineral series

Tsumcorite belongs to the helmutwinklerite group, whose members are

• tsumcorite PbZnFe2+(AsO4)2.H2O
• helmutwinklerite PbZn2(AsO4)2.2H2O
• thometzekite PbCu2+2(AsO4)2.2H2O
• mawbyite PbFe3+2(AsO4)2(OH)2 Tsumcorite forms a series with helmutwinklerite as Zn replaces the Fe2+, with thometzekite as Cu replaces the Zn and Fe2+,

Crystal habit and properties

Crystals are prismatic, elongated along the b axis, or wedge-shaped. They occur in radiating sheaves and spherulites, and as fibrous crusts or earthy and powdery material. Cleavage is good perpendicular to the c axis, and twinning is common.

Tsumcorite is yellow-brown, red-brown or orange in color, and it is one of the few minerals that have a yellow streak (orpiment and crocoite are two others). It is translucent, with a vitreous luster, and dichroic yellow to yellow-green. The optical class is biaxial and the refractive indices are approximately equal to 1.90.

The mineral is moderately hard, with a Mohs hardness of , between fluorite and apatite, and quite heavy, due to the lead content, with specific gravity 5.2, which is more than baryte but less than cerussite. It dissolves in hydrochloric acid and it is not radioactive.

Occurrence and associations

Tsumcorite is a rare secondary mineral in the oxidized zone of some arsenic-bearing hydrothermal lead-zinc deposits.

The type locality is the Tsumeb Mine, Tsumeb, Otjikoto Region, Namibia, where it is associated with willemite, smithsonite, mimetite, scorodite, anglesite, arseniosiderite, beaverite, beudantite, carminite, ludlockite, o'danielite, zincroselite, stranskiite and leiteite. At the Puttapa Mine in Australia it occurs with adamite, mimetite, smithsonite, goethite and quartz. At the Kintore Open Cut, Broken Hill, Australia it occurs with segnitite, beudantite, carminite and mawbyite.

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. Gaines et al (1997) Dana’s New Mineralogy Eighth Edition. Wiley
3. [http://www.mindat.org/min-4039.html Mindat.org]
4. [http://www.webmineral.com/data/Tsumcorite.shtml Webmineral data]
5. [http://www.handbookofmineralogy.org Handbook of Mineralogy]
6. Fleischer M (1972) New mineral names, American Mineralogist 57, 1558, being a summary of Geier, Kautz and Muller (1971) Neues Jahrbuch für Mineralogie (Monatshefte) 1971: 304–309
7. (1 December 1973). "The crystal structure of tsumcorite, a new mineral from the Tsumeb mine, S. W. Africa". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry.
8. There are two formula units per unit cell (Z = 2), and the [[space group]] is C2/m, meaning that the cell is a [[Bravais lattice|C-face centred lattice]], with lattice points in the center of the C face as well as at the corners of the cell.Crystallography (1993) Walter Borchardt-Ott, Springer Verlag

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