What is Garnet?

Garnet is a mineral resource that can be used in abrasives for industrial cutting and blast cleaning purposes; as jewellery and in other industrial uses like water filtration media.

 

Garnet can be found in a placer deposit or placer. It is where valuable minerals are accumulated or formed by gravity separation during sedimentary processes. A very small number of garnets are pure and flawless enough to be cut as gemstones. The majority of garnet mining is used to make abrasives.

 

Garnet is a dense and hard silicate mineral group. Garnet is actually a mineral group, not a single mineral:

  • the sg ranges from 3.58 (pyrope) to 4.32 (almandine)
  • they all have the same general chemical formula, X3Y2(SiO4)3
    • The different varieties of garnet have different metal ions
      • where X can be calcium, magnesium, ferrous iron, or manganese, and
      • Y can be aluminum, ferric iron, or chromium, or in rare instances, titanium.

Beach Garnet

Alluvial placers:

  • are formed by the deposition of minerals at a site where water velocity remains below that required to transport them further
  • usually formed in river or stream sediments like on the inside bends of rivers and creeks; at the break of slope on a stream; the base of a waterfall; etc.
  • Beach placers are formed in sand and gravel deposited along the edge of large bodies of water.

 

 

hard rock garnet

 

Skarn deposits:

  • are formed in the earth’s crust (metamorphic rocks) during transportation and reactions between adjacent rock units
  • usually calc-silicate minerals such as garnet and pyroxene are formed

 

The largest deposits are found in Australia, China and India. The Australian and Indian garnet deposits are mainly alluvial garnet from sea and rivers. In China, it is the rock garnet that dominates.

Hardness

  • Due to the varying chemical composition, the typical range of hardness on the MOHs scale is about 6.5 to 7.5
  • The harder species like almandine (7.5 MOHs) are often used for abrasive purposes. Diamond has a 10 MOHs hardness.