Dolomite: Carbonate
of Calcium and Magnesium. Calcium Carbonate 54%, Magnesium Carbonate
46%. This mineral is a form of Calcite and is used for many of the
same purposes. Much of the common white marble is Dolomite. It is
white, reddish or greenish-white, occurring in crystals and in all the
forms characteristic of calcite except the fibrous. Its streak is
always white, it is transparent or translucent, and is largely employed
as building and ornamental stone, massive dolomites being especially
deirable as building material. It is found in Switzerland, Mexico,
England, also in Vermont, Hoboken, N. J., Niagara Falls, Joplin, Mo.,
and North Carolina.
Domeykite: A Copper Arsenide. Arsenic 28.3%, Copper 71.7%. Occurs
massive and disseminated, color tin-white to steel-gray, becoming
covered with a yellow or brown tarnish when exposed to the air. It
occurs principally in Chile and is named after the Chilean
mineralogist, Domeyko. It also occurs in the Lake Superior regions and
in California and Mexico.
Dyskrasite: Silver
Antimonide. Comparatively rare mineral and composition doubtful on
account of the difficulty in obtaining pure material for analyses.
Occurs in foliated granular and structureless masses; twinning
frequent, yielding star-shaped aggregates. This mineral, which is a
good conductor of electricity, has a silver-white color and streak, but
its exposed surfaces are often tarnished yellow or black. It appears
principally in the silver mines of Central Europe, especially at Baden
and Harz, and also at Copiapo, Chile.
Ecdemite: Arsenate.
Arsenic 12.1%. Occurs in crystals, massive, coarsely foliated or
granular. Color bright yellow to green. Translucent in thin splinters.
Found at
Langban and Pajsberg, Sweden and Lake Valley, Mexico.
Electrum: An alloy of Gold and Silver. Gold containing silver
to a proportion of 20%. The word in Greek means
amber, and its use for this alloy is probably because of
the pale yellow color. This amber-colored alloy of gold and silver
was used by the ancient Greeks for coins, (see Gold).
Embolite: A grayish-green mineral containing both chloride and
bromide of Silver. The percentage varies in different
specimens, according to the color, the deeper green
colors containing the larger proportion of bromide. Abundant in
Chile, constituting the principal silver ore of the Chanarcillo Mines;
