Minerals streak

In an article on the life and mineral collection of Sir Hans Sloane, Jessie M. Sweet states that The only specimen which fortunately is still in the Mineral Collection is the original fragment of columbite (B. M. 60309), of which a brief account may be given here. Sloane describes it in the catalogue of Metalls, No. 2029, as A very heavy black stone with golden streaks. . . from Nautneague. From Mr. Winthrop (40). 

Among the most common surface X-ray scattering techniques used to probe mineral-fluid interface structure is the measurement of crystal truncation rods (CTRs). CTRs are diffuse streaks of intensity connecting bulk reciprocal lattice (Bragg) points in the direction perpendicular to a surface, and arise as a natural... 

Another form of the same oxide, in combination with water, ib very abundant as a mineral kDOWn as brown iron ore. It has a brownish color, produces a yellow streak, and, wheD crushed, a yellow powder it Is thus easily distinguished from the anhydrous oxide, which yields a red-brown powder. It is of lower specific gravity than the red, varying in density from 3-8 to 4-2. It usually occurs in a massive state, and is composed of—... 

The principal ore of toerenry is the sulphide—tho Annober of the Gormans and minium of Pliny. The color of native cinnabar varies from coehineal red to brownjsh-Ted and leaden grey. The.streak is scarlet, and the lustre usually adamantine. The density of this mineral is 8-098, and when pure it contains 86-29 parts of mercury with 13-71 of sulphur. Specimens of the purest ore have, occasionally,. all the richness of hue which the best vermilion presents. 

Its fracture is uneven or Imperfectly conchoids its streak white, and its specific gravity 4 34 to 4 45. The ore is infusible before the blowpipe, but affords a white sublimate of oxide of zinc, when it Is heated on tho charcoal, and which is yellowish while hot, and becomes white on cooling.. By moistening the assay with a solution of nitrate of cobalt, and then heating, the green color peculiar to zinc under such treatment makes its appearance. It is readily soluble In. acids with the evolution of carbonic acid, and in an excess of caustic potassa. Tho following analyses of a few samples.of the mineral indicate its composition —... 

A few years ago it was pointed out to me by Sterling Hendricks that ordinary black mica, biotite, which has an intensely black color, owes this color to the presence of iron in both the ferrous and ferric oxidation state. Black tourmalines also usually contain both ferrous and ferric iron. Another intensely black mineral, with black streak, is ilvaite, with composition Ca(Fe )aFe+++(Si04)20H. 

None of the lignocellulosic plant tissues in coal balls has been altered to vitrinite in any of the various European and American coal balls I have examined. It would be very interesting to know the source of Dr. Teichmuller s coal ball vitrinite reflectances. I believe they must refer to streaks of unmineralized peat which can be found associated between centers of coal ball mineralization which had been compressed and coalified rather than actually petrified. None of the plant material within coal balls I have examined can be taken as having any bearing on metamorphism or on the rank of the coal. 

Many mineral and synthetic samples examined by Bennett and Gard 17,18) gave typical C-centered orthorhombic diffraction patterns and with few exceptions had streaks in the hOl section, indicating an incomplete c-glide plane. A few crystals gave electron diffraction patterns having diffuse maxima in the hOl streaks, which could be interpreted as representing an I-centered mordenite structure. 

ALUNITE. The mineral alunite, KAl3(S04)2(0H)t , is a basic hydrous sulfate of aluminum and potassium a variety called natroalunite is rich in soda. Alunite crystallizes in the hexagonal system and forms rhombohedrons with small angles, hence resembling cubes. It may be in fibrous or tabular forms, or massive. Hardness, 3.5-4 sp gr, 2.58-2.75 luster, vitreous to pearly streak white transparent to opaque brittle color, white to grayish or reddish,... 

ANGLESITE, Naturally occumng lead sulfate (PbSQi), which crystallizes in the orthorhombic system and may be found mixed with galena, from which it is usually formed by oxidation. Hardness, 3 specific gravity, 6,12-6.39 luster, adamantine to vitreous or resinous transparent to opaque streak, white colorless to white or green, but rarely may be yellow or blue, This mineral is used as a source of lead. 

ATACAMITE. This mineral is a basic chloride of copper corresponding to formula Cu2Cl(OH)3. Crystallizes in thin, orthorhombic prisms, may occur massive. Hardness, 3-3.5 sp gr, 3.76-3.78 luster, adamantine to vitreous color, green, streak, green transparent to translucent. 

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. 

AZURITE. This mineral is a basic carbonate of copper, crystallizing in the monoclinic system, with the formula Cu2.(C03)2(0H)2, so called from its beautiful azure-blue color. It is a brittle mineral with a conchoidal fracture hardness. 3.5-4 sp gr, 3.773 luster, vitreous, color and streak, blue transparent to translucent Azurite, like malachite, is a secondary mineral, but for less common than malachite. It is formed by the action of carbonated waters on compounds of copper or solutions of copper compounds. 

BARITE. The mineral barite is barium sulfate, BaSOa crystallizing in the orthorhombic system. It may occur as tabular crystals, in groups, or lamellar, fibrous and massive, Barite has two perfect cleavages, basal and prismatic hardness, 3-3.5 specific gravity, 4.5, which has led to the term heavy spar, occasionally used for this mineral. Its luster is vitreous streak, white color, white to gray, yellowish, blue, red and brown transparent to opaque, it sometimes yields a fetid odor when broken or when pieces are rubbed togedier, due probably to the inclusion of carbonaceous matter. It is used as a source of barium compounds. 

BROCHANTITE. A mineral composed of basic copper sulfate corresponding to the formula Cut (S04)(OH)/, crystallizing in the monoclinic system in needle-like prisms, or forming druses or masses. Hardness, 3.5-4 specific gravity, 3.9 vitreous luster color, green streak, green transparent to translucent. 

CHRYSOBERYL. The mineral chrysoberyl. an aluminaie of hery Ilium corresponds to the formula BeALO. , crystallizes in the orthorhombic system with both contact and penetration twins common, often repeated resulting in ro.setted structures. Hardness. 8.5 specific gravity. 3.75 luster vitreous color various shades of green sometimes yellow. A variety which is red by transmitted light is known as alexandrite. Streak colorless transparent to translucent, occasionally opalescent. Chrysoberyl also is known as cymopbane and golden beryl. 

---