The angle across the water phase of an air-water-mineral system, used to
measure effect of surface conditioning. Pryor, 4
In geology, a bed lying next to or in contact with a formation of
different character. Fay
A breccia around an igneous intrusion, caused by wall-rock fragmentation
and consisting of both intrusive material and wall rock; intrusion
breccia. CF:agmatite
A mineral deposit between two unlike rocks. The term is usually applied to
an orebody at the contact between a sedimentary rock and an igneous rock.
See also:contact vein
A valley that has been eroded along a zone of weakness at the contact
between two different kinds of rock, as between two different sedimentary
formations, between igneous and sedimentary rocks, along a fault, or along
an upturned unconformity.
A protractor for measuring the angles between adjacent crystal faces.
See also:goniometer; reflection goniometer. Fay
The line of intersection of a contact surface with the surface of an
exposure or with the surface of bedrock covered by mantle rock; it may be
exposed or concealed.
In this type log, provision is made for electrodes to be pressed firmly
against the borehole wall. By doing this, current flowing from the
electrodes to the wall of the borehole no longer has to traverse the mud.
The path from the electrodes through the mud filter cake that sheaths
permeable beds is also reduced to a mininium. The electrode spacing of
contact logging devices is very small by comparison with the spacings used
in conventional logging devices. Consequently, contact logging devices see
very much more detail in the beds they pass through. Wyllie
A device that consists of a spring bow very analogous to a section gage.
On one arm of the bow is a rubber pad shaped to fit the curvature of the
hole. In this pad, slightly recessed, are three electrodes of about
diameter 1/2 in (1.3 cm) and located at 1-in (2.54-cm) intervals. These
three electrodes are used to record two resistivity curves. One curve is a
three-electrode type with a spacing of 1-1/2 in (3.8 cm), and the second
is a two-electrode type with a spacing of 2 in. Wyllie
Adj. of contact metamorphism.
Applied to rocks and/or minerals that have originated through the process
of contact metamorphism. AGI
A process taking place in rocks at or near their contact with a body of
igneous rock. Metamorphic changes are effected by the heat and materials
emanating from the magma and by some deformation connected with the
emplacement of the igneous mass. CF:thermal metamorphism;
metamorphic aureole. Approx. syn: pyrometasomatism. Adj:
contact-metamorphic. See also:exomorphism; endomorphism. AGI
A deposit formed by high-temperature magmatic emanations along an igneous
contact. Bateman, 2
A mass change in the composition of rocks in contact with an invading
magma, from which fluid constituents are carried out to combine with some
of the country-rock constituents to form a new suite of minerals.
AGI
A mineral formed by contact metamorphism.
A process for making sulfuric acid. Sulfur dioxide gas (obtained by
burning pyrite) is purified by electrical precipitation, and is passed
over a catalytic agent to form sulfur trioxide that combined with water
produces sulfuric acid. CTD
S. Afr. This term generally denotes the Ventersdorp contact reef, a
gold-bearing conglomerate beneath the Ventersdorp lavas and frequently
overlying mineralized horizons of the Witwatersrand system.
Beerman
The resistance observed between a grounded electrode and the ground, or
between an electrode and a rock specimen. AGI
Rocks produced by contact metasomatism. They include both the border rocks
of the intrusion and metamorphosed or recrystallized portions of the
intruded rocks, esp. limestone. See also:skarn; tactite.
Collector shoe, which maintains contact between the conducting wire or
rail and the electric vehicle being powered. Pryor, 3
a. The simplest type of twin, in which two portions of a crystal appear to
have been united along a common plane after one portion has been rotated
180 degrees relative to the other portion. The plane of contact (plane of
union or the composition face) may or may not be the twinning plane.
Syn:juxtaposition twin
b. A twinned crystal wherein the individual twins meet at a surface.
CF:interpenetration twin; penetration twin.