A general term which usually refers to ore minerals but which
often may refer to other metallic minerals such as pyrite.
Rock which is not ore. Usually referred to that rock which has
to be removed during the normal course of mining in order to get at the
The concentration of each ore metal in a rock sample, usually
given as weight percent. If concentrations are extremely low, as with
Au, Ag, Pt and others, the concentration may be given in grams per tonne
(g/t). The average grade of an ore deposit is calculated, often
employing very sophisticated statistical procedures, as an average of
the grades of a very large number of samples collected from throughout
The cut-off grade is the arbitrarily defined lowest grade
which will be mined from an ore ore deposit, and usually defines the
boundary of the deposit. For example, if the average grade of a porphyry
deposit is 0.5% Cu, the cut-off might be 0.2% Cu. any rock with a grade
below 0.2% Cu would be waste.
The amount of ore in a given deposit, usually quoted as the
number of tonnes available at a specific average grade.
The rock which surrounds the ore deposit. Also referred to as
wall rock , in particular that rock on either side of a vein.
Hot fluids, usually mainly water, sometimes acidic which may
carry metals andother compounds in solution to the site of ore
deposition or wall rock alteration.
A change in the mineralogy of the country rock as a result of
a chemical reaction with hydrothermal solutions. For example, mafic
minerals such as hornblende or biotite may alter to chlorite and
feldspars may alter to clay. An alteration zone describes rocks which
have been altered to a specific group of secondary or alteration
minerals, usually around the perimeter of a mineral deposit.
A tabular deposit usually formed by deposition of ore and
gangue minerals in open spaces within a fault or other structural
A chemical process whereby hydrothermal fluids, passing
through permeable rocks, react with the rocks to dissolve original
minerals and relace them with oreand/or other gangue minerals.
A stratiform (see below), usually lens-shaped mineral deposit
consisting of at least 60% sulphide minerals.
A replacement of limestone (calcium carbonate) or other
carbonate-rich rocks adjacent to an intrusive contact by calc-silicate
minerals usually through the addition of Si and other elements.
Mineralization which has been deposited later than its
immediate host rocks, for example a vein. The ore is younger than the
Mineralization which has been deposited simultaneously with
its host rocks, forexample placer deposits. The ore is the same age as
the host rocks.
A rusty, surficial weathering zone which is caused by the
oxidation of pyrite to produce secondary iron oxide minerals. Since
pyrite is often associated with ore deposits, gossans can be a guide to
The lower contact of an inclined vein, or the wall rock which
lies on the lower side of a dipping vein.
The upper contact of an inclined vein.
A planar feature or fracture zone along which displacement has
A planar zone of weakness, similar to a fault, but consisting
of several parallel displacement zones usually over a greater width than
a single fault.
All refer to mineralized zones within a fault or shear zone or
a vein fissure, stringer structure.
Angular fragments of rock produced by movement along a fault
or explosive igneous activity. The material which surrounds the
fragments and cements them together is called matrix and might be vein
minerals, igneous material or very fine rock fragments.
A large number of small, closely spaced veins, often with many
different orientations, is referred to as a stockwork and sometimes as a
Also referred to as a pipe , this is a vertically oriented,
cylindrical body, often a breccia, of vein or replacement
This is a horizontally oriented chimney-like structure,
usually of replacement mineralization.
Banding may represent small scale sedimentary layering in a
syngenetic deposit such as a massive sulphide or repeated pulses of
mineralization in a vein.
When minerals grow within a vein, they often grow inwards from
the vein wall. Several layers of different types of minerals,
representing different pulses of often aligned symmetrically away from
the center of the vein.
When minerals crystallize inwards from opposite walls of a
vein, they often meet in the center to form an interdigitating pattern
of crystals, usually quartz, which has an appearance similar to a
This is an open space or cavity, usually within a vein.
This is a crustiform banding when it surrounds breccia