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Formula: PbAl3(PO4)(PO3OH)(OH)6
Hydrated phosphate containing hydroxyl, plumbogummite group,
alunite supergroup
Crystal System: Trigonal
Specific gravity: 4.01
Hardness: 4½ to 5
Streak: White
Colour: Light blue, grey-white, yellow-grey, yellow, yellow-brown, red-brown, greenish, bluish, dark blue-grey
Solubility: Soluble in hot acids
Environments:
Plumbogummite is a relatively common secondary mineral in the
oxidised zone of lead deposits (HOM) often associated with
pyromorphite
and baryte, as well as mimetite,
duftite, cerussite,
anglesite and
wulfenite (HOM), and may be
pseudomorphic after
pyromorphite (common) or
baryte
Localities
At the Kintore Open Cut, New South Wales, Australia, plumbogummite occurs as a replacement of
fluorapatite grains in a
quartz-fluorapatite rock. It is also
found at this locality as veins enclosing hinsdalite, in
garnet
sandstone
(AJM 3.1.50).
At the New Cobar mine, New South Wales, Australia, plumbogummite occurs as small veinlets associated with
malachite, azurite,
cuprite and hematite
(AJM 11.2.78).
The Laohuan "mine", Laohu, Gongcheng county, Guilin, Guangxi, China, is a collection of artisanal adits and
excavations dug into the side of Laohu Hill, and originally worked for lead,
zinc, silver and
baryte, but commercial ore mining
there ceased long ago.
Laohuan is the world’s most important locality for plumbogummite. At the 2012 Tucson Show, several dealers
carried freshly collected lots of plumbogummite on yellow
mimetite/pyromorphite from
this locality. At the 2014 Ste.-Marie-aux-Mines show, several dealers had larger and better specimens of
plumbogummite over
mimetite/pyromorphite, with
underlying crystals to 5 cm, some of these being total pseudomorphic
replacements by plumbogummite. The 2014 Denver Show saw the first public displays of enormous, spectacular
specimens of the plumbogummite pseudomorphs after
pyromorphite, the grey-green to sky-blue plumbogummite ranging
from thin coatings over the pyromorphite crystals to total replacements,
in clusters to 16 cm across. The forms of the deeply hoppered original
pyromorphite crystals are faithfully preserved; the individual
pseudomorphic crystals reach 5.5 cm
(Minrec 53.6.697-732).
The plumbogummite pseudomorphs after
pyromorphite are sometimes very colourfully fluorescent, best
observed under mid-wave UV (303 nm). The plumbogummite shows bright green fluorescence with bright
orange accents provided by residual unaltered pyromorphite,
seen mainly at some of the crystal tips. A similar response is seen under short wave UV (254 nm) but the
orange pyromorphite response is more subdued burnt orange
colour. Under long wave UV (365 nm) a bright, monochromatic, pale blue fluorescence is seen. The daylight
colour is pale blue-green. The green fluorescence is probably activated by trace amounts of
(UO2)2+
(Minrec 54.4.364).
Plumbogummite from Laohuan - Image
At Yangshuo, Guangxi, China, plumbogummite occurs with
pyromorphite
(AESS), and plumbogummite pseudomorphs after
pyromorphite have been found
(KL p210).
Plumbogummite from Yangshuo - Image
At the type locality, Huelgoat, Brittany, France, plumbogummite occurs in a polymetallic lead vein with
pyromorphite,
cerussite, anglesite and
wulfenite
(Dana, Mindat).
Plumbogummite from Huelgoat - Image
At Dry Gill mine, Caldbeck, Allerdale, Cumbria, UK, plumbogummite occurs on
quartz with associated
pyromorphite
(AESS)
Plumbogummite from Dry Gill - Image
At Roughton Gill, Caldbeck, Allerdale, Cumbria, UK, plumbogummite occurs as encrustations on
quartz or
pyromorphite, occasionally overgrown by
mottramite, and also associated with
mimetite. It sometimes forms epimorphs after
pyromorphite at this locality
(JRS 11.20, Dana, MinRec 41.1.42).
Plumbogummite from Roughton Gill - Image
At the Mexico mine, Roughton Gill, Allerdale, Cumbria, UK, plumbogummite is associated with
pyromorphite
(MinRec 41.1.34).
At Burdell Gill, Mungrisdale, Eden, Cumbria, UK, plumbogummite has been found encrusting
goethite-coated
quartz, associated with or replacing
mimetite. It is also found as a coating on
beudantite crystals at this locality
(JRS 8(1).6).
At the Canton mine, Cherokee county, Georgia, USA, plumbogummite is associated with
marcasite
(Dana).
At the Upper dumps, North Star Mine, Mammoth, Tintic Mining District, Juab County, Utah, USA, plumbogummite
has been found on quartz matrix associated with
fluorapatite. One specimen of tan plumbogummite crystals that
was analyzed showed an unusual amount of tellurium. No further analysis
has been done, but this plumbogummite was found with a small black metallic fragment of
goldfieldite in a vug in
quartz
(MinRec 55.2.218).
Plumbogummite from the Upper Dumps -
Image
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