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Formula: PbFe3+3(AsO4)(AsO3OH)(OH)6
Hydrated arsenate,
dussertite group, forms a series with
beudantite
Crystal system: Trigonal
Specific gravity: >4.2
Hardness: 4
Streak: Pale yellow
Colour: Greenish to yellowish-brown
Environments:
Segnitite is an arsenic-bearing mineral.
Localities
At the Kintore opencut, Broken Hill South Mine, Broken Hill, Broken Hill district, Yancowinna Co., New South Wales,
Australia, segnitite is found in the oxidised zone of
lead-zinc sulphide ore bodies
where it overgrows beudantite on a matrix of
goethite encrusting quartz and
small spessartine crystals. It is also associated with
mimetite, carminite,
bayldonite, agardite-Y and
mawbyite
(Dana).
Segnitite from the Kintore opencut -
Image
At the Alto das Quelhas do Gestoso Mine, Gestoso, Manhouce, São Pedro do Sul, Viseu, Portugal, segnitite has
been found with lepidocrocite on
quartz
(Mindat photo).
Segnitite from the Alto das Quelhas do Gestoso
Mine - Image
In the Slitt Vein at Heights Pasture Mine, Weardale, County Durham, England, UK, segnitite has been found in the
supergene weathering zone in manganese oxide-rich pockets and as crusts on
quartz. The mine worked a substantial fluorite orebody
both underground and in a large surface excavation, and it is from this surface working that the segnitite was recovered.
The Slitt vein here cuts limestone and the overlying
sandstone and shale, and is composed
almost entirely of quartz with wide lenses of
fluorite. Galena occurs in very small amounts disseminated
within the quartz and fluorite. The segnitite
is clearly of supergene origin
(JRS 19.39-42).
At Roughton Gill, Cumbria, segnitite occurs with carminite and
beudantite in fractures in
quartz-rich rock
(JRS 11.22).
Segnitite from Roughton Gill -
Image
At the San Rafael Mine, Nevada, segnitite occurs as a crystalline aggregate in pods of oxidised
galena and anglesite with
kaolinite and covellite. In
the altered rock bordering the pods segnitite occurs with
scorodite, carminite and
mimetite, and with adamite in
pods of limonite
gossan.
Segnitite from the San Rafael Mine -
Image
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