Formula: (NH4)2[(UO2 )2(SO4)O2 ].H2 O
Uranyl sulphate, zippeite group
Crystal System: Orthorhombic
Specific gravity: 4.433 calculated
Hardness: 2½
Streak: Pale yellow
Colour: Yellow to yellowish orange
Luminescence: Dull green-yellow fluorescence under 405 nm laser light

Sedimentary environments
Hydrothermal environments


There are two co-type localities, the Burro mine, Slick Rock Mining District, San Miguel County, Colorado, USA, and the Blue Lizard mine, Red Canyon Mining District, San Juan County, Utah, USA.

At the Burro mine, Slick Rock Mining District, San Miguel County, Colorado, USA, larger and better crystals of ammoniozippeite were collected underground after they had first been found at the Blue Lizard mine (below). The Burro mine is located in a belt in which uranium and vanadium minerals occur together in bedded or rollfront deposits in sandstone. The uranium and vanadium ore mineralisation was deposited where solutions rich in uranium and vanadium encountered pockets of strongly reducing solutions that had developed around accumulations of carbonaceous plant material. Mining operations have exposed both unoxidised and oxidised uranium and vanadium phases. Under ambient temperatures and generally oxidising near-surface conditions, water reacts with pyrite to form aqueous solutions with relatively low pH (acid), which then react with the earlier-formed phases, resulting in diverse suites of secondary minerals.
Ammoniozippeite is rare at the Burro mine, where it occurs on a matrix consisting of bitumen, quartz and calcite, and is associated with gypsum, natrojarosite and natrozippeite (CM 56.235-245).

Ammoniozippeite from the Burro mine - Image

The Blue Lizard mine, Red Canyon Mining District, San Juan County, Utah, USA was where ammoniozippeite was first collected underground. Mineralised channels are in a member that consists of medium- to coarse-grained sandstone, conglomeratic sandstone beds, and thick siltstone lenses. Ore minerals were deposited as replacements of wood and other organic material and as disseminations in the enclosing sandstone.
Since the mine closed in 1978, oxidation of primary ores in the humid underground environment has produced a variety of secondary minerals, mainly sulphates, occurring as efflorescent crusts on the surfaces of mine walls.
At the Blue Lizard mine ammoniozippeite is more widespread than at the Burro mine, usually occurring on a matrix made up mostly of partially recrystallised quartz grains, which are remnants of the original sandstone. Ammoniozippeite has been found here with a wide variety of other secondary phases including blödite, bobcookite, brochantite, chalcanthite, devilline, dickite, ferrinatrite, gerhardtite, gypsum, johannite, kröhnkite, magnesiozippeite, natrozippeite, pentahydrite, pickeringite, plášilite, posnjakite, redcanyonite, wetherillite, and other potentially new uranyl sulphate minerals (CM 56.235-245).

Ammoniozippeite from the Blue Lizard mine - Image

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