Plumbogummite is a rare secondary lead
phosphate mineral, belonging to the
alunite
Alunite is a hydroxylated aluminium potassium sulfate mineral, formula K Al3( S O4)2(O H)6. It was first observed in the 15th century at Tolfa, near Rome, where it was mined for the manufacture of alum. First called ''aluminilite'' by J.C. Del ...
supergroup of minerals,
crandallite subgroup.
[ Some other members of this subgroup are:
* Crandallite, CaAl3(PO4)2(OH)5·H2O, where calcium replaces lead
* Goyazite, SrAl3(PO4)2(OH)5·H2O, where strontium replaces lead
* Philipsbornite, PbAl3(AsO4)2(OH)5·H2O, where the arsenate group AsO4 replaces the phosphate group PO4
Plumbogummite was discovered in 1819][ and named in 1832][ from the Latin "plumbum" for lead, and "gummi" for gum, in allusion to its lead content and appearance, which at times resembles coatings of gum.
]
Unit cell
Plumbogummite crystallizes in space group Rm. The reported lattice parameters (the lengths of the sides of the unit cell) vary in detail according to the source, but all agree that normal plumbogummite has "a" close to 7 Å and "c" close to 17 Å, with Z=3. Various reported values of "a" and "c"are:
:a = 7.01 Å,[ 7.017 Å,][ 7.018 Å,][ 7.033 Å][
:c = 16.71Å,][ 16.75 Å,][ 16.784 Å,][ 16.789 Å][
Mills ''et al.''][ investigated a ]gallium
Gallium is a chemical element with the symbol Ga and atomic number 31. Discovered by French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminiu ...
-rich sample of plumbogummite from Tsumeb, Namibia, and found larger cell parameters, with a = 7.0752 Å and c = 16.818 Å.
Structure
The basic structural units of plumbogummite are PO4 tetrahedra, with phosphorus atoms (P) at the center and oxygen atoms (O) at the corners, together with AlO6 octahedra, aluminium atoms (Al) at the center and oxygen atoms at the corners. The tetrahedra and octahedra combine by sharing corners, to form composite layers. Lead atoms (Pb) occupy sites between the layers.[
]
Environment
Plumbogummite is found in the oxidized zones of lead-bearing deposits. It commonly occurs as botryoidal, kidney shaped, stalactitic or globular crusts or masses, frequently with a concentric structure; rare crystals have a hexagonal outline. Pyromorphite and baryte
Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
are commonly associated minerals, and plumbogummite may be pseudomorphic after them. Other associated minerals include mimetite, duftite, cerussite, anglesite and wulfenite.[
]
Occurrence
The type locality
Type locality may refer to:
* Type locality (biology)
* Type locality (geology)
See also
* Local (disambiguation)
* Locality (disambiguation)
{{disambiguation ...
is Huelgoat, Finistère, Brittany, France, and the type material is stored in the Natural History Museum, Paris, France.[
Plumbogummite has been found in the Central Cobar Mines, New South Wales, Australia][Australian Journal of Mineralogy 11-2, 77] and the Nifty Copper Mine, Western Australia.[Australian Journal of Mineralogy 12-1, 28] Also in the Kintore open cut at Broken Hill, New South Wales
Broken Hill is an inland mining city in the far west of outback New South Wales, Australia. It is near the border with South Australia on the crossing of the Barrier Highway (A32) and the Silver City Highway (B79), in the Barrier Range. It is ...
, Australia, but it is generally inconspicuous there and only a few specimens have been collected.[Australian Journal of Mineralogy 3-1, 32 and 50]
Material from the Siglio XX Mine, Llallagua
Llallagua (in hispanicized spelling) or Llallawa (Aymara for a monstrous potato (like two potatoes) or animal, Quechua for the god of seed-time during the Inca period) is a town in the Potosí Department in Bolivia. It is the seat of the Llalla ...
, Bolivia, is an unusual pale yellow color, rather than the more common blue or green, forming crusts on quartz and cassiterite
Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains t ...
, and enclosing crude octahedral jeanbandyite crystals with orange colored shells of plumbogummite.[Mineralogical Record 37-2, 127 and 148]
References
{{Reflist
External links
The structure of Plumbogummite
Phosphate minerals
Lead minerals
Trigonal minerals
Minerals in space group 166
Crandallite group