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Formula: PbTe4+O3
Tellurite, triclinic paramorph
of monoclinic plumbotellurite
Crystal System: Triclinic
Specific gravity: Calculated 7.282 for the empirical formula and 7.313 for the ideal formula
Hardness: 2½
Streak: White
Colour: Light yellow
Solubility: Dissolves slowly in dilute hydrochloric acid at room temperature
Environments
Matthiasweilite is a new mineral, approved in 2021 and to date (June 2023) reported only from the type
locality.
Localities
The type locality is the mine dump of the Delamar mine, Delamar Mining District, Lincoln County, Nevada, USA. The mines
in this district principally exploited epithermal fissure veins composed mainly of
quartz and containing native gold, native
silver, pyrite,
chalcopyrite, bornite,
chalcocite, tetrahedrite,
tennantite, sphalerite and
galena, as well as baryte and
unidentified tellurides.
A wide variety of secondary minerals has been collected from several mine dumps, including numerous
tellurium oxysalts such as adanite,
bairdite, burckhardtite,
carlfriesite, choloalite,
emmonsite, eztlite,
fairbankite,
frankhawthorneite, jensenite,
khinite, kinichilite,
kuksite, leisingite,
mcalpineite, mojaveite,
mullerite, northstarite,
paratimroseite, poughite,
quetzalcoatlite,
rodalquilarite, spiroffite,
teineite, tellurite,
tlapallite, utahite,
xocolatlite, xocomecatlite
and possibly zemannite. Other minerals include native
tellurium, altaite, and likely
hessite.
Matthiasweilite was initially identified on a single micromount-sized specimen in a cavity in
quartz in direct association with
northstarite. It was subsequently identified on several other small
specimens in association with adanite,
choloalite and northstarite,
and in a polished thin section of partially oxidised primary ore,
where it occurs together with northstarite and other oxysalts in close
association with altaite,
tetrahedrite-(Zn), gold, and other
sulphides and selenides. It is interpreted to be a
secondary mineral crystallising from solutions rich in
lead and tellurium sourced from the
oxidation of primary lead
and tellurium minerals, such as galena,
altaite, hessite, and possibly
petzite.
Samples from the Delamar mine reveal a complex mixture of primary
sulphides, especially tetrahedrite, with relict
tellurides such as altaite and
selenides such as naumannite.
These have undergone deep weathering to produce a range of oxysalt minerals, varying from simple
lead - tellurium - oxygen phases such
as matthiasweilite, to complex lead -
iron - copper -
(selenium silver) -
antimony - tellurium - oxygen crusts.
On the holotype specimen, matthiasweilite occurs in tightly intergrown masses of crystals, these being ~0.35 mm
across, occupying cavities in quartz
(CM 60.805-814).
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