glauconitic sandstone

A sandstone containing sufficient grains of glauconite to impart a marked
greenish color to the rock; greensand. AGI

glaucophane

A monoclinic mineral, 2[Na₂ (Mg,Fe)₃ Al₂ Si₈ O
₂₂ (OH)₂ ] ; amphibole group with Mg/(Mg+Fe) = 0.5 to 1.0;
prismatic cleavage; bluish-gray to lavender blue; common in
low-temperature, high-pressure schists associated with lawsonite,
pumpellyite, or epidote. CF:crossite; riebeckite.

glaucophane schist

A type of amphibole schist in which glaucophane rather than hornblende is
an abundant mineral. Epidote frequently occurs, and there are quartz and
mica varieties. AGI

glaucopyrite

A variety of loellingite containing cobalt. See also:loellingite
Standard, 2

glazing barrel

A rotating barrel in which gunpowder is glazed with graphite.
Standard, 2

glebe

a. A tract of land containing mineral deposits or ore.
b. Obsolete term for a clod of earth, an ore, or an earthy mineral.
Arkell

Gleeds

A glowing coal or small coke such as that used in nailmaking. CTD

gleet

Slime, ooze, slimy alluvial deposit. Also spelled glet.

glessite

A brown variety of retinite; sp gr, 1.015 to 1.027; found on the shores of
the Baltic Sea.

gley soil

Soil developed under conditions of poor drainage, resulting in reduction
of iron and other elements and in gray colors and mottles. The term is
obsolete in the United States. AGI

glide

a. See:slip
b. A noncrystallographic shearing movement, as one grain over another.
ASM, 1
c. See:glide reflection

glide direction

a. The direction of gliding along glide planes in a mineral. AGI
b. The crystallographic direction of translation along a glide plane in a
space group; may be parallel to a crystallographic axis or along a
diagonal.
c. The crystallographic direction of slip along a slip plane in a single
crystal during plastic deformation. Syn:slip direction

glide plane

a. In single-crystal deformation, a plane on which translation- or
twin-gliding takes place without rupture during plastic deformation.
Syn:slip plane
b. The common plane of the two axes of a twin crystal. Hess
c. Slip plane or parting of mineral specimen. Direction along which slip
may occur under suitably directed pressure; due to weakness of bond in
crystalline structure along one of the three axes. Pryor, 3

glide reflection

See:glide

gliding

a. A change of form by differential movements along definite planes in
crystals without fracture. Fay
b. The formation of twin crystals. Hess
c. See:slip

gliding plane

See:slip plane

glimmer

See:mica

glimmerite

See:biotitite

glimmer plate

See:mica plate; accessory plate.

glimmerton

An early name for illite. Syn:illite

glinite

A group name for clay minerals from clay deposits. See also:chasovrite
AGI