Glossary

An autoclave is a machine that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel.

Non-ferrous, metals excluding precious metals. The term "base" indicates "low-born," i.e. of less worth. May also refer to metals that are the more easily corroded.

A metal oxide product produced from roasting or heating. For example a zinc calcine is an impure ZnO product obtained from roasting of a ZnS concentrate,

\[
\ce{ZnS_s + \frac{3}{2}O2_g = ZnO_s + SO2_g}
\]

Calcium oxide, CaO, is obtained by calcination of CaCO3:

\[
\ce{CaCO3_s = CaO_s + CO2_g}
\]

Any ion or neutral molecule which involves one or more metal ions and one or more coordinated ions or molecules, e.g. [Zn(H2O)6]+2, [AuCl4]3-, [Cu(CN)3]2-, Ni(CO)4, etc. (See Chemistry Review Part II).

The mineral of interest in a more concentrated form than was present in the ore. A variety of largely physical process (as opposed to processes that chemically alter the mineral) may be used to separate the desired mineral(s) from the surrounding rock. The result is a concentrate in which the desired minerals are present, but without much of the unwanted material. Generally the minerals remain in the original form. A concentrate may go on to leaching or pyrometallurgical extraction. Note that a concentrate refers to something distinctly different (mineral processing) from purification/concentration.

Electrolysis of a metal salt solution to produce metal.

A diagram depicting the sequence of steps and associated information for an chemical process.

The unwanted minerals that constitute the unwanted minerals of an ore. These are usually substantial fractions of the total mass.

Grade, or tenor, refers to the concentration of the minerals or elements of interest in the ore or deposit. Units may be % by weight, g/t, kg/t, oz/t (oz = ounces; the troy ounce is the common unit for precious metals. It equals 31.1034768 g.)

This refers to the individual mineral crystals in a deposit or sample.

Many minerals exhibit this property, which is variable composition within the same structure. This may occur when metal ions of similar size substitute for some of the principal metal ions. Some examples are pentlandite (Ni,Fe)9S8, in which variable amounts of nickel substitute for iron and powellite Ca(Mo,W)O4.

The ions or molecules that are coordinated to metal ions in complexes.

The earth's crustal rocks. The oceanic and non-oceanic lithospheres differ. In practice extractive metallurgy has used the land-based lithosphere. Oil and gas industries have made extensive use of the oceanic lithosphere.

The metal-enriched product from roasting in pyrometallurgical treatment of sulfide concentrates. The composition of matte from chalcopyrite (CuFeS2) roasting is roughly Cu2S·FeS.

Strictly speaking, a mineral is a naturally occurring, homogeneous inorganic substance of definite composition and crystal structure. Native elements (e.g. sulfur, gold) and compounds are included. A great many solid materials in nature fit this description. However, some solid materials have variable composition, e.g. pyrrhotite, FeS1-x and pentlandite, (Fe,Ni)9S8 where, respectively, varying fractions of iron and sulfur and nickel and iron occur. These are still considered minerals. Finally coal, which is not exactly an inorganic substance, nor of definite composition, may also be considered a mineral, broadly speaking.

A mineral deposit is a body of natural material that contains specific minerals.

The study of minerals: crystallography, chemistry, physical properties, classification and ways of distinguishing minerals. In the context of hydrometallurgy and mineral processing mineralogy refers to the type, concentration and distribution of minerals in a deposit. How the minerals are dispersed is very important. Gold may be present in the ore at a certain concentration, but is it localized between grains of silica or is it finely dispersed within a pyrite matrix? Issues like that make all the difference to how an ore is processed.

These are minerals which are a single chemical element. Examples are sulfur, mercury, antimony, copper, silver, gold, platinum, etc. Often these materials are not actually pure. They may be alloyed or combined with other elements to a minor extent. For example gold may contain some copper or silver.

The average concentration (in % by weight) of an element on the earth. (Strictly speaking it refers to the average concentration of any specified isotope. In hydrometallurgy the usual concern is with the average concentration including all naturally occurring, stable isotopes of an element.)

Metal elements that are not easily corroded; their simple cations have relatively high standard reduction potentials.

An ore is a mixture of minerals, one or more of which can be economically exploited as a source for one or more materials. These materials might ultimately be produced as metals, alloys, compounds or concentrates. Note that the key is economically viable production. This requires a certain grade of the mineral(s) to be present. Not all mineral deposits are ore bodies, but all ore bodies are mineral deposits. With advances in technology, or increases in price what was only a mineral deposit at one time, might become an ore later.

A concentration unit, usually mg (micrograms) of species of interest per kg of total mass of the sample. Since the density of water is nearly 1000 g/L (998 g/L at 21°C), and the density of a dilute solution is close to that of water, ppb is also often used synonymously with mg/L, though this is not strictly correct.

A concentration unit, usually mg (milligrams) of species of interest per kg of total mass of the sample. Since the density of water is nearly 1000 g/L (998 g/L at 21°C), and the density of a dilute solution is close to that of water, ppm is also often used synonymously with mg/L, though this is not strictly correct.

These include: Ru, Os, Rh, Ir, Pd, Pt. They are generally rare, noble metals and precious. PGM's and some of their compounds are noted for their catalytic properties.

The rare and highly valuable metals. Historically, Au, Ag, and PGM's. These also tend to be the metals that are less prone to corrosion. These in turn are known as the noble metals.

Various processes used to form a solid from solution. This may be a compound, such as Al(OH)3 after bauxite leaching and solution purification, or the metal itself, e.g. Cu metal produced from electrolysis of a CuSO4 solution.

The solution product of leaching, most commonly bearing the desired metals. Usually the metals are dissolved as cations (always with suitable counterions, like sulfate, SO42-), e.g. Cu+2, Zn+2 etc., or as complex ions, such as CuCl2-, Au(CN)2-, Zn(NH3)4+2, etc.

Process of heating and decomposing a mineral at high temperatures (pyrometallurgy). In sulfide roasting the sulfide is at least partially burned off, mostly as SO2 gas. Metal oxides, sulfates or sulfides with high (enriched) metal content may be produced.

A mixture of solution and solids. This is the state of an ore plus solution during and at the end of leaching. Complete dissolution does not occur.

The solid residue left after leaching. If this has further value it may be processed in subsequent steps. Otherwise it is waste. Tailings solids are often associated with wash water. The tailings mixture is stored or impounded in a tailings pond.

A common unit of mass when speaking of precious metals. 1 Troy ounce = 31.1034768 grams.

These are individual steps in an overall process. They are commonly understood in the industry, including the typical basic principles and procedures. A list of the general unit operations follows, along with associated terms. These overlap with elementary process units mentioned above. Unit operations are more concrete, well defined and specific.

This is the net amount of water that must be discharged from, or taken into a process. It is a critical parameter with respect to discharge of effluents and availability of process water in dry locations.