Arsendescloizite is a lead-zinc

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

, approved by the

IMA IMA or Ima may refer to: Education * Indian Military Academy, Dehradun * Instituto Miguel Ángel, a school in Mexico City Galleries and museums * Indianapolis Museum of Art, Indiana, US * Institut du Monde Arabe, Paris, France * Islamic Mus ...

in 1982. It is an

arsenate The arsenate is an ion with the chemical formula . Bonding in arsenate consists of a central arsenic atom, with oxidation state +5, double bonded to one oxygen atom and single bonded to a further three oxygen atoms. The four oxygen atoms orien ...

analog of descloizite. Its first description was published in 1982.

Properties

Arsendescloizite belongs to the adelite-

descloizite Descloizite is a rare mineral species consisting of basic lead and zinc vanadium, vanadate, , crystallizing in the orthorhombic crystal system and isomorphous with olivenite. Appreciable gallium and germanium may also be incorporated into the cr ...

group. It is the arsenate analog of the lead-zinc

vanadate mineral In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes and are referred to as hexacyanovanadate(III) and no ...

descloizite. It grows crystals that are platy to wedge-shaped. Its composition consists of lead (48.35%), oxygen (18.67%), arsenic (17.48%), zinc (18.99%), and contains a negligible amount of hydrogen (0.24%). Crystals are tabular on . These tabular crystals tend to intergrow into rose-like shaped aggregates. Observed forms are , , and . Unlike descloizite, arsendescloizite has no trace of vanadium in its composition whatsoever, thus it became quickly obvious that the mineral was from a new species. From the composition alone, this mineral could have also been the lead analog of

austinite Austinite is a member of the adelite-descloizite group, adelite subgroup, the zinc (Zn) end member of the copper-Zn series with conichalcite. It is the zinc analogue of cobaltaustinite and nickelaustinite. At one time “brickerite” was thoug ...

or the zinc analog of

duftite Duftite is a relatively common arsenate mineral with the formula CuPb(AsO4)(OH), related to conichalcite. It is green and often forms botryoidal aggregates. It is a member of the adelite-descloizite Group, Conichalcite-Duftite Series. Duftite and ...

. The specimen Pete and Paul were studying was found on a matrix of a copper ore that mainly consisted of

tennantite Tennantite is a copper arsenic sulfosalt mineral with an ideal formula . Due to variable substitution of the copper by iron and zinc the formula is . It is gray-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahed ...

. When studying the specimen, they found no trace of calcium or copper in its formula. This was weird due to the fact that it occurs with the calcium-rich mimetite and was found on a copper ore.

Occurrence

Arsendescloizite's type locality is at the Tsumeb mine, Namibia. It has been reported subsequently from

Cumbria Cumbria ( ) is a ceremonial county in North West England. It borders the Scottish council areas of Dumfries and Galloway and Scottish Borders to the north, Northumberland and County Durham to the east, North Yorkshire to the south-east, Lancash ...

, England. Arsendescloizite is also found in

Durango Durango, officially the Free and Sovereign State of Durango, is one of the 31 states which make up the Political divisions of Mexico, 32 Federal Entities of Mexico, situated in the northwest portion of the country. With a population of 1,832,650 ...

, Mexico. Arsendescloizite occurs in oxidized hydrothermal polymetallic deposits as a

secondary mineral A primary mineral is any mineral formed during the original crystallization of the host Igneous rock, igneous Primary Rock, primary rock and includes the essential mineral(s) used to classify the rock along with any accessory minerals. In ore deposi ...

. It is associated with

chalcocite Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system. T ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

mimetite Mimetite is a lead arsenate chloride mineral () which forms as a secondary mineral in lead deposits, usually by the Redox, oxidation of galena and arsenopyrite. The name derives from the Greek ''mimetes'', meaning "imitator" and refers to mimeti ...

goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α- polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...

and

willemite Willemite is a zinc silicate mineral () and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a vari ...

. It comes in a sequence of these minerals, arsendescloizite being between mimetite and goethite.

References

{{Reflist Arsenate minerals Orthorhombic minerals Lead minerals Zinc minerals Minerals described in 1982

Properties

Occurrence

See also

References