8.—AZURITE.
.
Occurs in crystals and masses with glassy lustre, or earthy and dull;
brittle; crackles and blackens, and finally fuses by heat; dissolves
with effervescence in nitric acid; gravity 3.5
Value.—A valuable ore of copper, containing sixty per cent.
Localities.—Found chiefly in lead and copper mines.
9.—Baryta, or Heavy Spar.
Occurs
in crystals, plates and masses; powder white; brittle; crackles when
strongly heated; not dissolved in acids; easily distinguished by its
weight ; gravity 4*5, or twice as heavy as Gypsum.
Value.—Used extensively as white paint and in pottery.
Localities.—Found in mining districts, often with lead, copper and iron ores, and in limestone.
10—Bituminous Coal.
Occurs in masses, beds or seams; softer and duller than Anthracite;
often a bright pitchy lustre; brittle, showing a slaty or jointed
structure rather than curved surface; powder black; burns readily with
yellow flame; by roasting forms coke; gravity 4. or less.
Value.—Used for fuel and the production of gas, coke, carbolic acid and aniline.
Localities.— Found west of Harrisburg, Pa. in rocks (slates and sandstones) less disturbed than in the Anthracite region.
11.—Blende.
Occurs
in crystals and masses; waxy lustre, but not always very apparent;
usual color, rosin-yellow to dark brown ; brittle; the powder, which is
whitish to reddish-brown, dissolves in muriatic acid giving off the
odor of rotten eggs; by roasting gives off sulphur-fumes; infusible
alone, but on charcoal at a high heat gives off white fumes; gravity 4.
Value.—An ore of zinc (containing sixty-six per cent.) and a source of white vitriol. Often worked for its Silver and Gold.
Localities,—Found with lead and other ores.
12.—Bog Iron Ore.
Occurs
in masses or beds, looking much like hard brown earth; loose or porous
and earthy, rather than compact and nodular; powder yellowish-brown;
when strongly heated becomes black and magnetic; gravity nearly 4. An
earthy yellow variety is called Yellow Ochre.
Value.—An important ore, yielding thirty-five pqr cent.
Localities.—Found in low, marshy grounds; widely distributed.
13.—Brittle Silver Ore.
Occurs
in crystals and masses; metallic lustre; tarnishes yellow, gray and
finally black; easily cut or broken; when heated gives off fumes of
sulphur and antimony, affording a button of silver; dissolved in nitric
acid, it silvers copper placed in it; gravity 6.
Value.—A rich ore of silver, containing over sixty per cent.
Localities.—Found in veins with other silver ores.
14.—Brown Coal.
Occurs like Bituminous Coal, but
usually brownish-black with less lustre, and often showing a woody or
slaty struf'ire; powder always brown; contains fossil plan's; gravity
between I'2 and 1.5
Value.—Inferior to No. 10. Makes no co'sc. Can be used in the manufacture of alum.
Localities.—Found in thin veins or elliptical mass?s, never in extensive layers.
