The transgression, across time planes or biozones, by a rock unit whose
age differs from place to place; the state or condition of being
diachronous. AGI
Said of a rock unit that is of varying age in different areas or that cuts
across time planes or biozones; e.g., said of a sedimentary formation
related to a narrow depositional environment, such as a marine sand that
was formed during an advance or recession of a shoreline and becomes
younger in the direction in which the sea was moving.
Syn:time-transgressive
An axial rotation of 180 degrees . Syn:twofold
A hydrated ferric phosphate and sulfate mineral, brown or yellowish in
color. Fay
Any change occurring within a sediment after its deposition and during and
after its lithification, exclusive of weathering. It includes such
processes as compaction, cementation, replacement, and crystallization,
under normal surficial conditions of pressure and temperature.
Deposits consisting dominantly of minerals crystallized out of sea water,
such as manganese nodules. Hunt
a. A mineral, such as olivine or quartz, whose presence in an igneous rock
indicates whether the rock is undersaturated or oversaturated. There are
also diagnostic minerals in sedimentary and metamorphic rocks.
Syn:symptomatic mineral
b. A mineral whose presence permits certain deductions pertaining to a
geologic history of a rock or sediment.
See:oblique fault
a. Joints diagonal to the strike of the cleavage. Zern
b. In igneous rocks, joints that occur at 45 degrees to the flow lines and
are caused by shear. Lewis
a. A compass used for surface and underground surveying. It is fitted with
sights, spirit levels, and a vernier, and mounted on a tripod.
Syn:mining dial
b. Corn. To make a mine survey. Pryor, 3
a. The process of running an underground traverse with a mining dial. Also
spelled: dialling. CTD
b. Surveying, usually magnetic, using miner's dial. Pryor, 1
A dark green or bronze-colored monoclinic pyroxene, which in addition to
the prismatic cleavages has others parallel to the vertical pinacoids.
Mohs hardness, 4; sp gr, 3.2 to 3.35. Used also as a prefix to many rocks
containing the mineral. See also:pyroxene
AGI; Webster 3rd; Fay
A former name for rhodochrosite.
A method of separating compounds in solution or suspension by their
differing rates of diffusion through a semipermeable membrane, some
colloidal particles not moving through at all, some moving slowly, and
others diffusing quite readily. CF:osmosis
See also:electrodialysis
Having a small, negative magnetic susceptibility. All materials that do
not show paramagnetism or magnetic order are diamagnetic. Typical
diamagnetic minerals are quartz and feldspar. CF:paramagnetic
AGI
The property of certain substances by virtue of which they are repelled
from both poles of a magnet and tend to set with the longer axis across
the lines of magnetic force. CF:ferrimagnetism; paramagnetism.
Standard, 2
See:diamondiferous
A circuit that employs two or more rectifying elements with a conducting
period of 180 electrical degrees, plus the commutating angle.
Coal Age, 1
a. An isometric mineral, a form of carbon, C ; crystallizes in octahedra,
dodecahedra, or cubes, commonly with curved edges and striated faces;
rarely twinned; has octahedral cleavage and conchoidal fracture. Fresh
cleavages have adamantine luster, but crystal faces are commonly greasy;
colorless when pure but pale tints to black (bort) with impurities. The
hardest natural substance, it defines 10 on the Mohs hardness scale and 15
on the Povarennykh scale, but ranges from 42 to 46 on a linearized Mohs
scale. Its high refractive index (n = 2.42) and strong dispersion give
fire to faceted gems. Diamond occurs in kimberlite pipes and dikes, also
in river and beach placers. See also:congos
b. A crystalline material resembling diamond such as rock crystal (quartz)
locally known as "Bristol diamond," "Herkimer diamond," "Lemont diamond,"
"Lake George diamond," or "Arkansas diamond."
See also:industrial diamonds; manmade diamond.
c. A pointed wooden or iron arrangement placed between rails, just before
a curve or switch, where tram cars are liable to be derailed, to force
them to remain on the rails. Fay
An important industrial variety of diamond. The stones are spherical
masses of minute diamond crystals arranged more or less radially. They
have no well-defined cleavage planes and thus have great resistance to
abrasion. While the term, ballas, was first applied to such stones from
Brazil, diamonds of similar structure known as Cape and African ballas are
found. In color, ballas ranges from white to varying shades of black.
While Cape and African ballas are not as hard as the Brazilian, they
include some fine and unusual stones. Production is small. Rarely, if
ever, used for diamond drilling but very valuable for diamond tools.
Cumming, 1