Mineral tetragonal

On beginning the investigation of the tetragonal pseudo-cubic mineral braunite, 3Mn303.MnSi03, we found the unit of structure to be closely related to that of bixbyite, and, indeed, to have dimensions nearly the same as those for two superimposed bixbyite cubes. This led us to... 

Red tetragonal crystal density 4.46 g/cm melts at 1,127°C vaporizes around 1,400°C sparingly soluble in water soluble in warm mineral acids decomposes in boiling water. Tetrahydrate is red orthogonal crystal density 2.22 g/cm3 decomposes on heating soluble in water di- and trihydrates are soluble in water. 

Transition metals play an important role in heterogeneous catalysis where reactions occur on the surfaces of metal or oxide crystals. Typical of these metals are V or Mo which exist in oxides with tetrahedral, tetragonal pyramidal, or octahedral coordination and which can change their oxidation states with minimal changes in their coordination environment. As in the case of soil minerals (Section 13.4.1), bond valences can be used to determine the bonding strength of the anions on the surface, by noting how far the valence sums around the surface ions fall short of 2.00 vu. 

An insoluble sulphate may be detected by the formation of turpeth mineral on the addition of a 10 per cent, solution of mercuric nitrate in dilute nitric acid (1 in 100) the small yellow tetragonal crystals of the basic sulphate may be identified microscopically. The reaction takes place immediately in the cold with calcium and mercurous sulphates, less readily with strontium and lead sulphates, whilst with barium sulphate boiling is necessary. ... 

Tellurium dioxide is known in two different crystalline forms. Crystals of the tetragonal system,2 but almost regular (a c — 1 1-1076), of density 5-66, are obtainable from the solution in nitric acid, while the molten dioxide when slowly cooled deposits rhombic needles 3 (a b c=0 4566 1 0-4693) of density 5-93 and identical with the rarely occurring mineral tellurite. 

Many sulfide minerals have structures closely related to those of sphalerite and wurtzite. Chalcopyrite, CuFeS, is an example (Fig. 11-21). Its structure 0 is a tetragonal superstructure of sphalerite, with the copper and iron atoms in the zinc positions of sphalerite. 

Calcium Boroarsenate occurs in New Jersey as the mineral cahnite4 (see p. 14) it forms white, vitreous, tetragonal sphenoids, occurring in characteristic interpenetrating twins. The refractive index is 1-662. 

ANATASE. The mineral anatase, TiC>2 crystallizing in the tetragonal system is a relatively uncommon mineral. It occurs as a tri-morphous form of Ti02 with rutile mid brookite. Rutile and anatase have tetragonal crystallization brookite, orthorhombic. Hardness, 5.5-6 sp. gr. 3.82-3.97 brittle with sub-conchoidal fracture color, shades of brown, into deep blue to black also colorless, grayish, and greenish also transparent to opaque with adamantine luster. 

AUTUNITE. This mineral is a hydrous phosphate of calcium and uranium, crystallizing in the tetragonal system, usually in thin tabular crystals. Good basal cleavage hardness. 2-2.5 specific gravity, 3.1 luster, subadamantine to pearly on the base color, lemon yellow streak, yellow transparent to translucent strongly fluorescent. 

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