Plumbogummite [SEP] named after
Plumbogummite
Plumbogummite is a rare secondary lead phosphate mineral, belonging to the alunite supergroup of minerals, crandallite subgroup. Some other members of this subgroup are:
- Crandallite, CaAl(PO)(OH)·HO, where calcium replaces lead
- Goyazite, SrAl(PO)(OH)·HO, where strontium replaces lead
- Philipsbornite, PbAl(AsO)(OH)·HO, where the arsenate group AsO replaces the phosphate group PO
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:
Mills "et al." investigated a gallium-rich sample of plumbogummite from Tsumeb, Namibia