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Formula: Sn2+21O6(OH)14Cl16
Hydroxyhalide, tin-bearing mineral
Crystal System: Trigonal
Specific gravity: 4.42 measured, 4.417 calculated
Hardness: 2
Streak: White
Colour: Colourless
Solubility: Dissolves rapidly in nitric acid and slowly in hydrochloric acid Dana
Environments
Abhurite is formed from the reaction of pure tin with sea water, and has
exclusively been associated with tin ingots from shipwrecks. Common associates
include aragonite, kutnohorite
and romarchite (Mindat). Under the natural saline conditions typical
of seawater, romarchite or
hydroromarchite is the stable phase; with higher salinity and reduction
in pH (more acid environment), the formation of abhurite is favoured
(AM 78.235-236).
Localities
At the type locality, Sharm Abhur Cove, Jiddah, Mecca Region, Saudi Arabia, the tin
ingot on which the abhurite crystals are found is principally tin, alloyed
with minor amounts of copper, lead,
bismuth, zinc and
antimony. The larger crystals of abhurite form within blisters or pods
that contain a viscous mass of liquid and solids. The fluid has an acidity (pH) of 1 (strongly acid). The pods, which
cover all the surfaces of the ingot, are up to to 10 mm in size. Abhurite crystals that are unprotected by the
blisters formed on the surface of the ingot and were interrupted in their development by a covering of
romarchite and a subsequent precipitation of
kutnohorite, aragonite and
coral. Most of the abhurite contains fragments of the tin alloy and other
crystallites
(CM 23.233-240).
The Queen Anne's Revenge wreck site, Beaufort, Carteret county, North Carolina, USA. Pewter, a
tin-rich alloy, has been widely used for ornamental and utilitarian purposes for
the last 400 years because it is durable, relatively easily worked, resistant to corrosion, and similar to silver in
appearance. Pewter plates and implements have been recovered and examined from what is believed to be the wreck site of
the Queen Anne’s Revenge, flagship of the pirate Blackbeard, that sank near Beaufort, North Carolina in 1718. All of the
pewter artifacts from the site display a surface veneer of corrosion products and may be viewed as experiments on
tin corrosion that have been continuously in operation for more than 280 years.
The corrosion products are composed of romarchite,
hydroromarchite and abhurite. The corrosion generally develops
in crudely concentric layers, with an inner layer of abhurite in contact with the pewter; the overlying outer
layers consist of romarchite and
hydroromarchite. Abhurite also occurs as masses of equant grains
with abundant small inclusions of residual pewter. Romarchite may be a
metastable phase, and is present as the result of slow process of the formation of
cassiterite, the most stable tin oxide
in most natural environments
(CM 41.659-669).
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