Appendix:Dictionary of Mining, Mineral, and Related Terms/A/5

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available alumina

The theoretical amount of extractable aluminum oxide, Al (sub 2) O (sub 3) , present in a bauxite. The amount of alumina in a bauxite that is present in a form that allows it to be extracted by a refining plant.

available energy

That part of the total energy that can be usefully employed. In a perfect engine, that part which is converted to work.

available lime

a. Those constituents of a lime that enter into a desired reaction under the conditions of a specific method or process.

b. Represents the total free lime (CaO) content in a quicklime or hydrate and is the active constituent of a lime. It provides a mean of evaluating the concentration of lime.

available power

The rate at which a given source would deliver energy to a load having an impedance that is the conjugate of the source impedance is designated as the available power of that source.

available power loss

The available power loss of a transducer connecting an energy source and an energy load is the transmission loss measured by the ratio of the source power to the output power transducer.

available relief

a. The vertical distance between the altitude of the original surface after uplift and the level at which grade is first attained.

b. The relief that is available for erosion.

available silica

The amount of silica present in a flux that is not slagged by impurities in the flux itself.


A large mass of snow, ice, soil, or rock, or mixtures of these materials, falling, sliding, or flowing very rapidly under the force of gravity. Velocities may sometimes exceed 500 km/hr.

avalanche protector

Guardplates that prevent loose material from sliding into contact with the wheels or tracks of a digging machine.


Alternate spelling of aventurine.


a. A word used to describe the metallic spangled effect seen, in reflected light, in aventurine and aventurine feldspar. A sort of schiller but more scintillating.

b. A display of bright or strongly colored reflections from included crystals in some translucent mineral specimens.


a. A glass containing opaque sparkling particles of foreign material, which is usually copper or chromic oxide. With copper particles, it is called gold aventurine, and with chromic oxide particles, it is called chrome aventurine or green aventurine. A glass containing gold-colored inclusions.

b. A translucent quartz that is spangled throughout with scales of mica or of some other mineral. Syn: aventurine quartz. c. As an adj., having the brilliant spangled appearance of aventurine. Applied esp. to transparent or translucent quartz or feldspar containing shiny inclusions. d. A variety of albite with reddish reflections from exsolved hematite in certain planes. See also: goldstone. Syn: sunstone; love stone.

aventurine feldspar

Orthoclase, albite, or oligoclase that is more or less transparent, with fiery reflections from enclosed flat mineral particles, which are probably hematite or goethite. Sunstone is aventurine oligoclase.

aventurine glass

A glass supersaturated with either iron, chromium, or copper oxide (or a combination of the oxides) that is melted and cooled under controlled conditions to cause the excessive oxides to crystallize, forming platelike crystals or spangles. See also: goldstone.

aventurine quartz

See: aventurine.

average assay value

See: assay value.

average clause

Eng. A clause that, in granting leases of minerals (coal, ironstone, and clay in particular), provides that lessees may, during every year of the term, make up any deficiency in the quantity of coal, etc., stipulated to be worked, so as to balance the dead or minimum rent.

average loading

The average number of tons of a specified material to be carried by a conveyor per hour, based on total operating-shift tonnage.


An isometric mineral, Tl (sub 2) O (sub 3) ; black; forms minute crystals.


Letter name specifying the dimensions of bits, core barrels, and drill rods in the A-size and W-group wireline diamond drilling system having a core diameter of 30.1 mm and a hole diameter of 48 mm. Syn: AX.


An isometric mineral, Ni (sub 2) Fe to Ni (sub 3) Fe . Syn: native nickel-iron.


Letter name specifying the dimensions of core, core barrels, and casing in the A-size and X-series wireline diamond drilling system having a core diameter of 30.1 mm and a hole diameter of 48 mm. The AX designation for coring bits has been replaced by the AW designation. Syn: AW.


a. Crystallographic directions through a crystal; used as lines of reference.

b. Reference coordinates a, b, c, in crystallography, crystallographic axes. c. Directions of apparent isotropy in anisotropic crystals, optic axes. d. Elements of rotational symmetry, symmetry axes. e. In ellipsoids representing the Fletcher indicatrix of refractive indices, semiaxes represent optic directions. Singular: axis. Also called optic axes.

axial angle

a. The acute angle between the two optic axes of a biaxial crystal. Its symbol is 2V.

b. The axial angle in air (symbol 2E) is the larger angle between the optic axes after being refracted on leaving the crystal. c. See: optic angle.

axial compression

In experimental work with cylinders, a compression applied parallel with the cylinder axis. It should be used in an appropriate sense only in the interpretation of deformed rocks.

axial element

In crystallography, the ratio of a unit distance along a crystallographic axis and the corresponding angle between axes. Syn: lattice parameter.

axial figure

a. The interference figure that is obtained in convergent light when an optic axis of the mineral being observed in thin section or as a fragment coincides with the axis of the polarizing microscope. When a thin section of a uniaxial mineral that was cut at right angles to an optic axis is examined between crossed nicols (that is, between two polarizers, the polarization planes of which are at right angles to each other) an equal-armed shadowy cross and a series of spectrally colored, circular bands are seen. If the mineral is biaxial, two shadowy parabolic curves called isogyres and opening away from each other in a series of spectrally colored, oval bands appear.

b. In polarized light microscopy, an interference figure in which an optic axis is centered in the field of view.

axial flow

In pumping or in ventilation, the use of a propeller or impeller to accelerate the load along the axis of the impeller.

axial-flow compressor

A compressor in which air is compressed in a series of stages as it flows axially through a decreasing tubular area.

axial-flow fan

a. A type of mine fan in which the mine air enters along the axis parallel to the shaft and continues in this direction to the point of exhaust. The axial-flow fan may have fixed blades (fixed-pitch fan) or adjustable blades (variable-pitch fan). Two, four, or six aerofoil section blades (like an aircraft wing) are usually employed. Also called a screw fan. CF: radial-flow fan; mixed-flow fan. See also: contra-rotating axial fan; mine-ventilation fan.

b. The compressed-air auxiliary fan consists essentially of a single-stage axial-flow fan in which the rotor also forms the rotor of a compressed-air turbine. The exhaust from the turbine is added to the ventilating air. The result is a light and very compact machine, capable of the same duties as the smaller sizes of electric auxiliary fans.

axial line

See: axis.

axial plane

a. A more or less planar surface that intersects a fold in such a manner that the limbs of the fold are symmetrically arranged with reference to it.

b. The plane of the optic axes of an optically biaxial crystal. c. A crystallographic plane that includes two crystallographic axes. d. Of geologic structures, a plane that intersects the crest of the trough or a fold such that the limbs, or sides, of the fold are more or less symmetrically arrayed with reference to it.

axial-plane cleavage

Cleavage that is closely related to the axial planes of folds in the rock, either being rigidly parallel to the axes, or diverging slightly on each flank (fan cleavage). Most axial-plane cleavage is closely related to the minor folds seen in individual outcrops, but some is merely parallel to the regional fold axes. Most axial-plane cleavage is also slaty cleavage.

axial-plane folding

Large-scale secondary folding of preexisting folds, in response to stresses that varied considerably from those that caused the original folding. The axial planes of the original folds are folded.

axial-plane foliation

Foliation that developed parallel to the axial plane of a fold and perpendicular to the principal deformational pressure.

axial-plane separation

The distance between axial surfaces of adjacent antiforms and synforms where the folds occur in the same layer or surface.

axial priming

A system for priming blast agents in which a core of priming material extends through most or all of the blasting agent charge length.

axial ratio

The lengths of crystallographic axes defined in terms of their ratios with, by convention, a set at unity where one axis is unique and b set at unity where all three axes are required.

axial stream

a. The main stream of an intermontane valley, which flows along the lowest part of the valley and parallel to its long dimension, in contradistinction to the streams that flow down the mountains on either side.

b. A stream that follows the axis of an anticline or a syncline.

axial trace

The intersection of the axial plane of a fold with the surface of the Earth or any other specified surface.


a. The mineral group ferroaxinite, magnesioaxinite, manganaxinite, and tinzenite.

b. Triclinic borosilicates with the formula A (sub 3) Al (sub 2) BSi (sub 4) O (sub 15) (OH) where A = (Ca,Fe,Mg,Mn). Syn: glass schorl.


A term proposed by Zirkel for a variety of elongated spherulite in which there is an aggregation of minute acicular crystals arranged at right angles to a central axis rather than from a point.


a. The central or dominating region of a mountain chain, or the line that follows the crest of a range and thus indicates the most conspicuous part of the uplift.

b. The centerline of a tunnel. c. Intersection of the axial plane of a fold with a particular bed; axial line. d. A straight line about which a body or a three-dimensional figure rotates or may be supposed to rotate; a straight line with respect to which a body, figure, or system of points is either radially or bilaterally symmetrical. e. In crystallography, one of the imaginary lines in a crystal that are used as coordinate of axes of reference in determining the positions and symbols of the crystal planes. CF: crystallographic axes; coordinate system. f. Often used synonymously with anticlinal; thus, the Brady's bend axis for Brady's bend anticlinal. See also: anticlinal axis; synclinal axis. g. The trace of the axial surface of a fold on the fold profile plane (obsolete). h. A line that follows the trend of large landforms, e.g., the crest of a ridge or mountain range, or the bottom or trough of a depression. Plural: axes.

axis of acoustic symmetry

For many transducers, the three-dimensional directivity is such that it may be represented by the surface generated by rotating a two-dimensional directivity pattern about the axis corresponding to the reference bearing of the transducer. This axis may then be described as an axis of acoustic symmetry or as the acoustic axis.

axis of symmetry

An imaginary line in a crystal, crystal structure, or crystal lattice, about which it may be rotated to an identical configuration. If identity occurs once during a complete rotation of 360 degrees , the axis is a monad, twice a diad, thrice a triad, four times a tetrad, or six times a hexad. Syn: symmetry axis.

axonometric projection

A method of projection which has the advantage of containing a true plan, and can therefore be set up from drawings already in existence for other purposes. The plan is turned through 45 degrees , vertical lines being drawn from the angles on the plan to show the elevations. See also: oblique projection; isometric projection.


In crystallography, having cleavage perpendicular to an axis; said of minerals.


A variety of nephrite jade. Also spelled axestone.


Direction of a horizontal line as measured on an imaginary horizontal circle, the horizontal direction reckoned clockwise from the meridian plane of the observer, expressed as the angular distance between the vertical plane passing through the point of observation and the poles of the Earth and the vertical plane passing through the observer and the object under observation. In the basic control surveys of the United States, azimuths are measured clockwise from south, a practice not followed in all countries. CF: bearing.


A variety of altered zircon. See: zircon.

Aztec stone

a. A greenish variety of smithsonite.

b. A green variety of turquoise.


Small cloudy sapphires occuring with diamonds in Brazil.


See: azurlite.


See: lapis lazuli; lazurite.

azure malachite

See: azurmalachite.

azure quartz

See: sapphire quartz.

azure spar

See: azurite; lazulite.

azure stone

A term applied to lapis lazuli (lazurite) and to other blue minerals such as lazulite and azurite.


a. A monoclinic mineral, 2[Cu (sub 3) (OH) (sub 2) (CO (sub 3) ) (sub 2) ]; forms vitreous azure crystals; a supergene mineral in oxidized parts of copper deposits associated with malachite; an ore of copper. Syn: azure spar; chessylite; blue copper; blue copper ore; blue malachite.

b. A compact semiprecious stone derived from compact azurite and used as a decorator material. c. A trade name for a sky-blue gem variety of smithsonite.

azurite malachite

See: azurmalachite.


Chalcedony colored blue by chrysocolla; and used as a gemstone. Syn: azurchalcedony.


An intimate mixture or intergrowth of azurite and malachite, commonly massive and concentrically banded; used as an ornamental stone. Syn: azure malachite; azurite malachite.