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Formula: NaCu2+Fe3+2(VO4)3
Anhydrous vanadate,
howardevansite group
Crystal System: Triclinic
Specific gravity: 3.814 calculated
Streak: Red-brown
Colour: Black
Common impurities: Al,Mn,Ti
Environments
Although howardevansite was approved in 1987, to date (April 2025) it has been reported only from the type
locality.
Localities
The type locality, the Izalco Volcano, Sonsonate Department, El Salvador, is a Holocene (11,700 years ago until
the present)
basalt-andesite volcano
that has been intermittently active since its formation in 1770. The fumaroles of the volcano have been a rich source
of high-temperature vanadium minerals. The minerals form as sublimates from a
vanadium halogen or oxyhalogen gas that was exsolved from a
basaltic magma when the magma was 550 m below the summit crater; at the
fumaroles, the vanadium compounds sublimed at temperatures up to
800oC.
Howardevansite has been discovered in the summit crater fumaroles, occuring with
lyonsite and thénardite, formed
as sublimates from the volcanic gases. Howardevansite occurs as euhedral, black tabular crystals; hundreds of
crystals are available, all less than 100 microns in greatest dimension
(AM 73.181-186).
Howardevansite from the Izalco Volcano -
Image
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