On basis of ir time of formation relative to host rock, ore deposits are divided into two groups: syngenetic and epigenetic.

Natural concentration of an ore mineral in a massive rock body is defined as an ore deposit. Hence definition of an ore deposit is also size dependent.

The three essential conditions for formation of hydrormal deposits are: highly active and enriched fluids, suitable pathways for ir migration through rocks, and suitable physic-chemical environment for ir deposition to take place.

Epigenetic deposits are those deposits that were formed subsequent to formation of host rock. Epigenetic deposits of igneous, sedimentary and metamorphic types are known.

The term, stock works, is used for hydrormal deposits that occur in veins or fissures of exceptionally small size, but in good number, within a limited space, traversing body of rock profusely.

Pegmatite deposits are sometimes classified as a distinct group of magmatic deposits formed towards end of crystallization process and such necessarily occurring close to roofs of magmatic masses.

Gash-veins are narrow, sloping and thick-bodies deposits of minerals deposited in solution-fissures or cracks of host rock which is generally a carbonate rock like limestone.

Syngenetic deposits are such deposits that have formed simultaneously with enclosing rock. These are eir of igneous or of sedimentary types.

Magmatic ore deposits commonly occur in following forms: segregations, disseminations and injections.

Fissure-veins may be defined as mineral bodies of elongated or tabular shape deposited in pre-existing fissures. The original fissures may be parallel or intersecting, radial or fan-shaped in pattern and that is also shape of resulting ore bodies.