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Formula: NaLa2(CO3)2[F2x(CO3)1-x]F
Anhydrous carbonate containing halogen
Crystal System: Hexagonal
Specific gravity: 4.072 calculated
Hardness: 3 to 3½
Colour: Beige, beige-yellow, light lemon-yellow, pinkish
Luminescence: Not fluorescent under long wave or short wave UV
Solubility: Slowly dissolves in dilute hydrochloric acid
Environments
Volcanic igneous environments
Hydrothermal environments
Arisite-(La) is a relatively new mineral, approved in 2009 and to date (July 2023) reported only from the
type locality.
Localities
At the type locality, the Aris Quarries, Aris, Windhoek Rural, Khomas Region, Namibia, arisite-(La) is a
layered rare-earth-element fluorcarbonate mineral from miarolitic cavities within
phonolite. It occurs as distinct chemical zones mixed with
arisite-(Ce). Crystals are vitreous, transparent beige, beige-yellow,
light lemon-yellow to pinkish, and occur as tabular prisms up to 1.5 mm
(MM 74.257-268).
Arisite-(La) is a late-stage, post-magmatic to hydrothermal mineral in miarolitic cavities as
lanthanum-rich cores in
arisite-(Ce) from
phonolite associated with an alkaline volcanic province.
Associated minerals include villiaumite,
aegirine, analcime,
apatite, fluorite,
manganoneptunite,
microcline, natrolite,
sphalerite,
tuperssuatsiaite, the Fe-analogue of
zakharovite and
arisite-(Ce)
(HOM).
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