Nagyagite: Sulpho-telluride
of Lead and Gold. Contains about 63% Lead, Telluride 13%, Gold 7%,
Antimony 7%. Exact formula uncertain. Occurs in tabular crystals,
also granular massive. Streak and color blackish lead-gray. It
occurs at Nagyag, Transylvania.
Natrocalcite: A
pale-yellow variety of Calcite; exterior smooth and hard, interior
cavernous. Occurs in Thuringia, Chile, and in Bisbee, Arizona.
Natrolite: Sodium
Silicate. This mineral occurs in acicular crystals, and in radial
fibrous, granular and dense masses. It is white or colorless,
yellowish, gray or reddish, transparent to translucent. Crystallized
Natrolite is abundant in volcanic rocks in Baden; in the basalts of
Bohemia and Silesia; in Tyrol, Italy and France. It occurs also in Nova
Scotia, Michigan, Arkansas and New Jersey.
Naumannite: A
Selenide of Silver and Lead. Selenium 27%, Silver 73%—sometimes
contains lead. This mineral occurs in cubes, in thin plates, also
massive and granular, color and streak iron-black. It was named after
the crystallographer and mineralogist, C. F. Naumann, and occurs
principally in Harz.
Nephelite:
Silica 44%, Alumina 33%. Composition varies. Occurs usually in thick
six or twelve-sided prisms, also massive and compact and in embedded
grains. It is colorless, white or yellowish, and when massive, green,
bluish-gray or brownish-red. It is found in the lava of Vesuvius, in
Prussia and Norway. Massive forms are found in Maine, New Hampshire,
Arkansas and Montana.
Nephrite: A
finely fibrous Actinolite or Tremolite. Its color is white or light
green and was formerly much used like Jade, in the manufacture of
charms and implements. The name is derived from the Greek meaning
kidney, and the stones were worn as a cure for diseases of the kidneys.
Nephrite was brought in the form of carved ornaments from Mexico and
Peru soon after the discovery of America.
Niccolite: Nickel Arsenide. Arsenic 56%, Nickel 44%. Occurs
massive usually, though crystals are known. It is pale
copper-red with a gray to black tarnish. It is found
with native Silver and Cobalt, at Cobalt, Ontario; in Europe it is
abundant in Bohemia Although rich in nickel, the mineral is not
