Arsendescloizite is a lead-zinc

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

, approved by the IMA in 1982. It is an

arsenate The arsenate ion is . An arsenate (compound) is any compound that contains this ion. Arsenates are salts or esters of arsenic acid. The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As(V). Arsenate resem ...

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

Properties

Arsendescloizite is a member of the

adelite The rare mineral adelite, is a calcium, magnesium, arsenate with chemical formula CaMgAsO4OH. It forms a solid solution series with the vanadium-bearing mineral gottlobite. Various transition metals substitute for magnesium and lead replaces cal ...

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

group. It is the arsenate analog of the lead-zinc vanadate mineral 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 in descloizite, arsendescloizite has no trace of vanadium in its composition whatsoever, thus it became obvious quickly 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 tho ...

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, tetrahedri ...

. 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 and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. Cumb ...

, England. Arsendescloizite is also found in

Durango Durango (), officially named Estado Libre y Soberano de Durango ( en, Free and Sovereign State of Durango; Tepehuán: ''Korian''; Nahuatl: ''Tepēhuahcān''), is one of the 31 states which make up the 32 Federal Entities of Mexico, situated in ...

, 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 primary rock and includes the essential mineral(s) used to classify the rock along with any accessory minerals. In ore deposit geology, hypogene processe ...

. 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. The ...

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

mimetite Mimetite is a lead arsenate chloride mineral (Pb5(AsO4)3Cl) which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name derives from the Greek Μιμητής ''mimetes'', meaning "imitator" a ...

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