A product of the action of sulfuric acid on clay, consisting chiefly of
silica and aluminum sulfate. Webster 3rd
An argillaceous rock, commonly a shale, containing marcasite or pyrite
which, as it decomposes, forms sulfuric acid that attacks the shale and
produces alum. Many such rocks are carbonaceous. See also:alum shale
Hess
An oxide of aluminum, Al2 O3 ; the mineral corundum; an
important constituent of clay minerals, Al2 Si2 O5
(OH)4 , determining their suitability for firebrick and furnace
linings. Synthetic alumina is used as the feed material in aluminum
smelters; it is also used in the preparation of paints called lakes, in
dyeing, and in calico printing; in granular form it is used for abrasives
and grinding or cutting tools of high tensile strength. Most alumina is
made via the Bayer process from hydrated aluminum oxides, as found in
bauxite, diaspore, and gibbsite. Aluminum oxide can also be made in an
electric furnace by fusing bauxite or corundum. Suitably doped alumina is
the feed material for boules of synthetic ruby and sapphire made by the
Verneuil flame-fusion process. Fused alumina is crushed and used as an
abrasive, a refractory, a heating element for electrical heaters, and as a
filtering medium.
A compound having the general formula, MAlO2 or M3 AlO (sub
3) , in which M indicates a monovalent metal. Mineral aluminates, such as
MgAl2 O4 , are termed spinels. Bennett
A2 O3 .3H2 O or Al(OH)3 ; monoclinic; white;
crystalline powder, balls, or granules; sp gr, 2.42; obtained from bauxite
and used as a source of aluminum. CCD, 2; Lee
A monoclinic mineral, Al2 (SO4 )(OH)4 .7H2 O ;
pseudo-orthorhombic, formerly called websterite. Syn:alley stone;
argil.
A general term that includes all refractories of the fireclay,
sillimanite, mullite, diaspore, and bauxite types. Dodd
An abrasive produced by fusing aluminum oxide. Mersereau, 2
Ore in which the gangue consists principally of alumina. Osborne
A light, silvery-white, ductile metal with high electrical conductivity
and good resistance to corrosion. Obtained from bauxite. Symbol, Al. It is
the lightest of the metals in general use commercially and is the basis
for light alloys used in the construction of modern aircraft and rockets;
aluminum coatings are used for telescope mirrors, decorative paper,
packages, and toys. The oxide, alumina, occurs naturally as ruby,
sapphire, corundum, and emery. Handbook of Chemistry and Physics, 3
See:Briska detonator.
Varying proportions of Al2 O3 and SiO2 . Occur
naturally in clays. Used in the glass and ceramics industry.
CCD, 2
See:alunite
A variety of opal with alumina and lime as impurities. Fay
An amorphous aluminum hydroxide that is a constituent of bauxite. Formerly
called cliachite, diasporogelite, and sporogelite.
See:alunite
Natural salt from which alum can be made. See also:halloysite;
kaolinite. Sanford
See:alum shale
An argillaceous, often carbonaceous, rock impregnated with alum,
originally containing iron sulfide (pyrite, marcasite) which, when
decomposed, formed sulfuric acid that reacted with the aluminous and
potassic materials of the rock to produce aluminum sulfates.
Syn:alum earth; alum schist; alum slate. AGI
See:alum shale
a. A trigonal mineral, KAl3 (OH)6 (SO4 )2 ;
massive or disseminated; in pale tints; formed from sulfuric acid acting
on potassium feldspar in volcanic regions (alunization), and around
fumaroles. Formerly called alumstone, alum rock, alumite.
b. A mineral group including jarosite.