Cornwallite
Copper arsenate mineral
title: "Cornwallite" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["arsenate-minerals", "monoclinic-minerals", "minerals-in-space-group-14"] description: "Copper arsenate mineral" topic_path: "general/arsenate-minerals" source: "https://en.wikipedia.org/wiki/Cornwallite" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Copper arsenate mineral ::
::data[format=table title="infobox mineral"]
| Field | Value |
|---|---|
| boxbgcolor | #65c131 |
| boxtextcolor | #fff |
| image | Cornwallite-178955.jpg |
| imagesize | 260px |
| caption | Cornwallite in a vug from Pastrana, Murcia, Spain (size: 4.3 × 3.7 × 2.2 cm) |
| category | Arsenate mineral |
| formula | Cu5(AsO4)2(OH)4 |
| IMAsymbol | Cnw |
| strunz | 8.BD.05 |
| dana | 41.4.2.2 |
| system | Monoclinic |
| class | Prismatic (2/m) |
| (same H-M symbol) | |
| symmetry | P21/c |
| unit cell | a = 17.33 Å, b = 5.82 Å, |
| c = 4.60 Å; β = 92.22°; Z = 2 | |
| color | Verdigis green, blackish-green, emerald-green |
| habit | Microcrystalline radial fibrous, botryoidal to globular crusts |
| cleavage | Distinct in one direction |
| fracture | Conchoidal |
| tenacity | Brittle |
| mohs | 4.5 |
| luster | Sub-vitreous, resinous, waxy |
| streak | Apple green |
| diaphaneity | Translucent to opaque |
| gravity | 4.17 |
| opticalprop | Biaxial (+/−) |
| refractive | nα = 1.810 – 1.820 nβ = 1.815 – 1.860 nγ = 1.850 – 1.880 |
| birefringence | δ = 0.040 – 0.060 |
| 2V | Measured: 30° to 50° |
| references | |
| :: |
|boxbgcolor=#65c131| name = Cornwallite | boxtextcolor = #fff | image = Cornwallite-178955.jpg | imagesize = 260px | alt = | caption = Cornwallite in a vug from Pastrana, Murcia, Spain (size: 4.3 × 3.7 × 2.2 cm) | category = Arsenate mineral | formula = Cu5(AsO4)2(OH)4 | IMAsymbol = Cnw | strunz = 8.BD.05 | dana = 41.4.2.2 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = P21/c | unit cell = a = 17.33 Å, b = 5.82 Å, c = 4.60 Å; β = 92.22°; Z = 2 | color = Verdigis green, blackish-green, emerald-green | habit = Microcrystalline radial fibrous, botryoidal to globular crusts | twinning = | cleavage = Distinct in one direction | fracture = Conchoidal | tenacity = Brittle | mohs = 4.5 | luster = Sub-vitreous, resinous, waxy | streak = Apple green | diaphaneity = Translucent to opaque | gravity = 4.17 | density = | polish = | opticalprop = Biaxial (+/−) | refractive = nα = 1.810 – 1.820 nβ = 1.815 – 1.860 nγ = 1.850 – 1.880 | birefringence = δ = 0.040 – 0.060 | pleochroism = | 2V = Measured: 30° to 50° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = Cornwallite is an uncommon copper arsenate mineral with formula Cu5(AsO4)2(OH)4. It forms a series with the phosphate pseudomalachite and is a dimorph of the triclinic cornubite. It is a green monoclinic mineral which forms as radial to fibrous encrustations. ::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/ba/Cornwallite-Baryte-54193.jpg" caption="Botryoidal, green cornwallite in a [[gossan]] with white [[baryte]] from [[Caldbeck Fells]], [[Cumbria]] (7.6 × 5.1 × 4.7 cm)"] ::
Discovery and occurrence
It was first described in 1846, for an occurrence in Wheal Gorland, St Day United Mines of the St Day District, Cornwall, England. It occurs as secondary mineral in the oxidized zone of copper sulfide deposits. Associated minerals include olivenite, cornubite, arthurite, clinoclase, chalcophyllite, strashimirite, lavendulan, tyrolite, spangolite, austinite, conichalcite, brochantite, azurite and malachite.
References
References
- Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
- [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cornwallite Mineralienatlas]
- [http://rruff.info/doclib/hom/cornwallite.pdf Cornwallite in the Handbook of Mineralogy]
- [http://www.mindat.org/min-1133.html Cornwallite on Mindat.org]
- [http://www.webmineral.com/data/Cornwallite.shtml Cornwallite data on Webmineral]
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