Ore and Gangue:  The general definition of “ore” is a naturally occurring material from which minerals of economic value can be extracted at a profit.  Stating the commodity for which it is mined, for example “gold ore” or “iron ore”, often modifies the term “ore”.   Ore minerals are the specific minerals containing the commodity of interest.  Many minerals contain elements of commercial interest, but are not ore minerals because the mineral is “refractory”, meaning it is difficult to impossible to extract the commodity from the mineral.  “Gangue minerals” refer to material so intimately associated with ore that it has to be mined with it, and later removed by various crushing, grinding and separation processes.  The “host rock” is the rock surrounding the ore and gangue, which, like the gangue, has no value.  To illustrate these relationships, consider the following example for a gold ore:

Ore Deposits:  An “ore deposit”, or “ore body”, is a continuous, well-defined mass of material containing a sufficient volume of ore to mine economically.  In other words, the length, width and thickness must be determined as well as the concentration of the commodity of interest.  Defining an ore body (ore deposit) generally requires drilling to determine the thickness as well as the depth below the surface.

Ore Minerals:  Ore minerals are typically categorized as either “metallic” or “nonmetallic” (also called “industrial”).  Metallic minerals, as the name implies, are minerals containing metals.  We refer to the common metals, which are chemically active and commonly alloyed, as “base metals” (eg, copper, lead and zinc).  In contrast, “precious metals” are rare metals with high commercial value commonly desired in their isochemical form (eg, gold, silver, platinum).  Nonmetallic minerals are of course all other types of minerals.     

Lode Deposits:  Ore deposits can are broadly broken down into two groups, called “lode” and “placer”.  Lode deposits are those that occur within consolidated rock, having formed during the original formation of the rock, or some time after that.   The processes which form lodes are often implied to be chemical in nature, whether it was due to the original fluids within a magma, or the magma itself, or whether it was due to some hydrous (water rich) fluids which migrated through the rock at a later date and altered its original composition. 

Placer Deposits:  In contrast, a placer deposit is formed in inconsolidated material, and forms as a result of physical processes at or near the earth’s surface.  The processes are secondary in nature and the prime example is weathering.  In some environments the climatic and hydraulic (action of water) conditions are just right to create a natural mechanical concentration process.  The most typical environment is the stream environment.  Where this concentration happens, the unconsolidated sediments in the stream can become enriched enough with valuable  minerals to be classified as ore deposits.  A large amount of gold is mined from this type of deposit, called a placer gold deposit.

Disseminated:  Minerals which are scattered as small particles throughout a rock.

Vein:  A tabular or sheetlike mineral deposit often filling a fracture or fault.

Aggregate: Crowded or massed together into a dense cluster.

Opaque: Does not allow light to pass through.

Mineralization: To develop a mineral formation

Consolidation: United into one form.

Foliation: Consecutive thin layers