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nablock

A rounded mass, as of flint in chalk, or of ironstone in coal.
Standard, 2

nacre

The hard, iridescent internal layer of various mollusk shells, having
unusual luster and consisting chiefly of calcium carbonate in the form of
aragonite deposited as thin tablets normal to the surface of the shell and
interleaved with thin sheets of organic matrix. Syn:pearly;
mother-of-pearl. AGI

nacreous

Adj. Applied to the luster of certain minerals, usually on crystal faces
parallel to a good cleavage, the luster resembling that of pearls.
CMD

nacrite

A monoclinic mineral, Al2 Si2 O5 (OH)4 ;
kaolinite-serpentine group; differs from other kandites, such as triclinic
kaolinite and monoclinic dickite, in the stacking order of its layers
(polytypy); fine-grained, massive; commonly associated with hydrothermal
alteration.

nadir

a. The point on the celestial sphere that is directly beneath the observer
and directly opposite the zenith. AGI
b. The point on the ground vertically beneath the perspective center of an
aerial-camera lens. AGI

nadorite

An orthorhombic mineral, PbSbO2 Cl ; an uncommon secondary mineral;
in resinous to adamantine crystals in some base-metal deposits.

naetig

Industrial diamond having a grain in all directions instead of in regular
layers. CF:feinig

nagyagite

A possibly orthorhombic mineral, Pb5 Au(Te,Sb)4 S5-8;
occurs with other tellurides in lamellar, soft, heavy, lead-gray
crystals; one perfect cleavage but may form anhedral masses.
Syn:black tellurium

nahcolite

A monoclinic mineral, NaHCO3 ; forms small, white, highly soluble,
prismatic crystals; in nonmarine evaporite deposits; esp. abundant in
parts of the Green River lake beds of Colorado.

naif

adj. Said of a gemstone having a true or natural luster when uncut; e.g.,
of the natural, unpolished faces of a diamond crystal. Also spelled naife.

nail

a. See:shooting needle
b. A slender piece of metal, one end of which is pointed, the other end
having a head, either flattened or rounded. It is a common means of
fastening together several pieces of wood or other material by striking
the head with a hammer. The term penny as applied to nails refers to the
number of pounds per 1,000 nails; e.g., six-penny nail means 6 lb (2.7 kg)
per 1,000; three-penny means 3 lb (1.4 kg) per 1,000, etc. Crispin

nailhead spar

A composite variety of calcite having the form suggested by the name.
Fay

naked

See:bare; blank hole.

name of lode

The name by which a lode is designated in the notice of location, and
subsequent addition thereto is immaterial. The same vein or lode may have
different names in different mining locations. Ricketts

nanotesla

See:gamma

Nansen bottle

An oceanographic water-sampling bottle, made of a metal alloy that is
little reactive with seawater, equipped with a rotary valve at each end so
that when it is rotated at depth the valves close and lock shut,
entrapping a water sample and setting the reversing thermometers. This
bottle is named for its designer, Fridtjof Nansen. Hy

nantokite

An isometric mineral, CuCl ; granular, massive; cubic cleavage; adamantine
luster; an uncommon secondary mineral in copper deposits.

naphtha

a. An archaic term for liquid petroleum. AGI
b. Designates those hydrocarbons of the lowest boiling point (under 250
degrees C) that are liquid at standard conditions, but easily vaporize and
become flammable. They are used as cleaners and solvents. AGI

naphtha gas

Illuminating gas charged with the decomposed vapor of naphtha.
Standard, 2

naphthode

Concretion of bituminous limestone rich in carbonaceous matter.
Tomkeieff

Napierian logarithm

A natural logarithm. Webster 3rd