Image Credit: RRUFF Database Project (La Fuente et al. 2015; RRUFF ID R080007)
Mineral Species
Talmessite
Type Locality
No
Composition
Ca2Mg(AsO4)2·2H20
Crystal System
Triclinic
Status at Tsumeb
Confirmed
Abundance
Extremely rare
Distribution
Undetermined
Paragenesis
Supergene
Entry Number
Species; TSNB342
General Notes
Talmessite forms two series with gaitite, and with anorthoroselite (formerly roselite-β).
A specimen in the Pinch Collection (now at Harvard University; MGMH 2020.7.775) comprises colourless to pale yellow composite crystals of talmessite (to approximately 9 mm) associated with colourless-white calcite. The talmessite has been verified by single crystal XRD and EMPA and is included in the RRUFF database (https://rruff.info/talmessite/display=default/R080007; accessed August 2022).
Talmessite, confirmed by EDS and XRD, has also been reported from Tsumeb by Franz Neuhold (http://www.mindat.org/locentry-617558.html; accessed April 2015). Neuhold posted a photograph of a c. 130 μm crystal aggregate with colour zoning from orange-brown to lilac-pink. A portion of this specimen was verified by single crystal XRD. Neuhold suggested that compositions approaching gaitite or anorthoroselite may be represented within this same aggregate. (https://www.mindat.org/photo-1126647.html ; accessed August 2022).
Associated Minerals
anorthoroselite; calcite; gaitite
