A foliated or scaly white pearly variety of calcite. Syn:earth foam;
foam spar. Standard, 2; Fay
See:stevensite
Said of the texture of a fine-grained or aphanitic igneous rock that lacks
phenocrysts. Also, said of a rock exhibiting such texture. AGI
A lens free from both chromatic aberration and spherical aberration.
See also:achromatic
A lens free from spherical aberration. CF:aberration
See also:aplanachromatic lens
A light-colored igneous rock characterized by a fine-grained saccharoidal
(i.e., aplitic) texture. Aplites may range in composition from granitic to
gabbroic, but the term aplite with no modifier is generally understood to
mean granitic aplite, consisting essentially of quartz, potassium
feldspar, and acid plagioclase. The term, from a Greek word meaning
simple, was in use before 1823. Syn:haplite
glass manufacture. AGI
a. Pertaining to the fine-grained and saccharoidal texture characteristic
of aplites. AGI
b. Said of an igneous rock having such a texture. AGI
A light-colored rock of granitic texture consisting essentially of alkali
feldspar and quartz, with subordinate biotite; muscovite may be present or
absent. CF:two-mica granite; alaskite. Holmes, 1
A nongelatinous permissible explosive. Used in coal mining.
Bennett
A method of roasting carbonate iron ore in a shaft furnace. The ore sinks
continuously down the furnace while a current of hot air or flue gas, with
a low carbon dioxide content, is passed through the body of the ore and a
current of cold air is passed upward through the lower part of the shaft,
this part acting as a cooling chamber for the ore and as a preheating flue
for the air, which rapidly oxidizes the ferrous oxide in the upper regions
of the furnace. The quantity and temperature of the hot gases and cold air
are carefully regulated, so as to keep the carbon dioxide content of the
flue gas at a minimum and thereby ensure thorough roasting of the ore at
the lowest possible temperature. A furnace roasting 181 to 408 t/d
requires about 176,400 to 220,500 kg.cal/t (736 to 923 kg.kJ/t), giving a
heat efficiency of 73%. Osborne
Said of a hydrothermal mineral deposit at an intermediate distance from
its magmatic source. The term is little used. CF:telemagmatic;
cryptomagmatic. AGI
A mineral group, 2[KFCa4 (Si8 O20 ).8H2 O]
(fluorapophyllite) with F replaced by (OH) (hydroxyapophyllite) and K
replaced by Na (natroapophyllite); occurs in square micaceous crystals as
secondary minerals in cavities in igneous rocks. Syn:fisheye stone
See:tongue
A rhyolite, the groundmass of which was once glassy but has become
devitrified.
The coal-producing area extending from northern Pennsylvania to Alabama,
in and adjacent to the Appalachian Mountains.
a. Late Paleozoic Era diastrophism beginning perhaps in the Late Devonian
Period and continuing until the end of the Permian Period. AGI
b. A period of intense mountain-building movements in the late Paleozoic
Era, during which the deposits in the Appalachian and Cordilleran
geosynclines were folded to form the Appalachian and Palaeocordilleran
mountains. Equivalent to the Armorican and Hercynian movements in Europe.
Syn:Appalachian revolution
a. In soil mechanics, the resistance of particles to being pulled apart,
due to the surface tension of the moisture film surrounding each particle.
Also called moisture film cohesion. Hunt
b. Cohesion in granular soils due to capillary forces.
See also:cohesion
a. The weight (W) of an object or material divided by its exterior volume
(Ve ) less the volume of its open pores (Vp ). Apparent
density = W/(Ve - Vp ). ACSG, 2
b. Weight per apparent volume. See also:density
Van Vlack
The dip of a rock layer as measured in any exposed section, or direction,
not at a right angle to the strike. It is a component of, and hence always
less than, the true dip. See also:angle of dip; true dip; dip.
Stokes
The apparent movement observed in any chance section across a fault is a
function of several variables: the attitude of the fault; the attitude of
the disrupted strata; the attitude of the surface upon which the fault is
observed; and the true movement (net slip) along the fault. AGI