A polygon having eight sides. Jones, 2
A rhombohedral form of hydrous sodium borate, Na2 B4 O (sub
7) .5H2 O , simulating regular octahedrons. From the Lagoong of
Tuscany, Italy. See also:tincalconite
In the isometric system, cleavage parallel to the faces of an octahedron.
Fay
See:cuprite
See:magnetite
a. A class of meteorites. Hey, 1
b. The most common iron meteorite contains 6% to 18% nickel in the metal
phase; on etching, shows Widmanstaetten structure owing to the presence of
intimate intergrowths (of plates of kamacite with narrow selvages of
taenite) oriented parallel to the octahedral planes.
c. A former name for anatase. See also:titanium dioxide
a. A closed crystallographic form with isometric symmetry and eight faces,
each an equilateral triangle; sometimes called a regular octahedron to
distinguish it from the more general usage defined below. Commonly
observed in isometric minerals, such as fluorite, pyrite, magnetite, and
diamond.
b. Less precisely, a closed crystallographic form composed of (or bounded
by) eight triangular surfaces (a bipyramid), such as in some samples of
anatase. Plural: octahedra. Adj.: octahedral.
Each eighth of crystal space divided by three noncoplanar axial planes.
CF:dodecant
Used to limit the number of sample data points used for estimating
intermediate spatial values. The search neighborhood is divided into eight
equal-angle sectors. Constraints on selection of data values to include in
the estimation include: minimum and maximum of samples or the number of
consecutive empty sectors. If either criteria is below minimum, an
interpolated value is not calculated. Applies to any interpolation method
where a limited number of sample data points are used to estimate
intermediate values.
a. A trioctahedral clay mineral. AGI
b. A group of mica minerals that contains eight cations per ten oxygen and
two hydroxyl ions.
c. Any mineral of the octaphyllite group, such as biotite; a trioctahedral
clay mineral. CF:heptaphyllite
A bin or tank to facilitate the concrete lining of circular shafts. The
concrete is mixed on the surface, taken down the shaft in buckets, and
discharged into the octopus. The concrete is then led away through
flexible rubber pipes to different points around the shaft. Nelson
Eyepiece of a microscope. Pryor, 3
A formula used for calculating the thickness of tubbing: t = hdF/2C + A,
where: t is the required thickness of tubbing in inches; h is the pressure
of water in pounds per square inch; d is the diameter of the shaft in
inches; C is the crushing strength of cast iron in pounds per square inch,
which may be taken as 95,000; F is the factor of safety adopted between 5
and 10; and A is the allowance for possible flaws and corrosion and may
vary from 1/4 to 1 in (6.4 to 25.4 mm), averaging 1/2 in (12.7 mm).
Sinclair, 2
A mine subsidence theory based on an extension of the theory of the
normal. In it, subsidence is regarded as taking place in two stages. There
is, first, a breaking of the rocks in which the lines of fracture tend to
run at right angles to the stratification. This is followed by an
aftersliding, or inward movement from the sides, resulting in a pull or
draw beyond the edges of the workings. Briggs
A fossil bone or tooth colored deep blue by iron phosphate (vivianite),
and rarely green by copper compounds, and resembling turquoise, such as
that from the tusks of mammoths found in Siberia. It is cut and polished
for jewelry. Syn:bone turquoise; fossil turquoise. AGI
a. The practical, cgs electromagnetic unit of magnetic intensity. A unit
magnetic pole, placed in a vacuum in which the magnetic intensity is 1 Oe
(79.577 A/m), is acted upon by a force of 1 dyn in the direction of the
intensity vector. AGI
b. Commonly used as the cgs unit of magnetic-field intensity. Except in
magnetized media, a magnetic field with an intensity (H) of 1 Oe has an
induction (B) of 1 Gs (0.1 mT). AGI
A method of shaft sinking by freezing wet ground in sections as the
sinking proceeds. The permanent lining is also inserted as the shaft is
sunk. The freezing equipment is a cylinder equal in diameter to the shaft
and 44 in. (1.12 m) in height, with the lower end closed by a plate. The
cylinder is in sections, each of which can be removed. Each section is
provided with freezing coils. After freezing the ground, two sections are
removed, the ground is thawed locally and removed, and a segment of the
permanent lining is inserted. The process is repeated.
See also:Dehottay process; freezing method. Nelson
A waterway port in a noncoring diamond bit, not located in the center of
the bit face. Long
N. of Eng. One of the goaf roadways in longwall workings, which are set
about 120 yd (110 m) apart. Fay
A truck of such size, weight, or dimensions that it cannot be used on
public highways.
The expression in a patent according to the official plat of survey of the
land returned to the general land office by the surveyor general refers to
the description of the land as well as to the quantity conveyed.
Ricketts