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How to Rate Garnet Stones

January's birthstone, the garnet, refers to several species and varieties of minerals. Usually considered dark red, garnets can come in many colors, from the ruby red pyrope to the deep green dematoid variety. Garnets are a semiprecious stone with a 6.5 to 7.5 Mohs scale rating for hardness, with a diamond rating 10. The Gemological Institute of America (GIA) classifies the stone as a type 2 for clarity, indicating the presence of internal flaws. Although there is no industry-wide clarity scale for rating garnets, most gemologists use a version of the GIA rating system.

Things You'll Need

Garnet
Magnififying glass, ratio 10-to-1

Instructions

- 1
  Review the GIA Type 2 clarity ratings for garnets in the Gemstones and Jewelry website.
  
  VVS1: Extremely fine quality; few inclusions and hardly detectable under magnification.
  
  VVS2: Extremely fine quality; minor inclusions.
  
  VS1: Very fine quality; tiny inclusions not affecting the gem's overall quality.
  
  VS2: Fine quality; barely visible inclusions not affecting the gem's overall clarity.
  
  SI1: Good quality, lightly included; inclusions are visible without magnification but do not reduce visual beauty of the stone.
  
  SI2: Medium to good quality, lightly included; easily visible inclusions viewed without magnification.
  
  I1, I2, I3: Medium to lower quality, included; easily visible inclusions viewed without magnification and affecting the stones overall beauty.
- 2
  Inspect the garnet for visible inclusions looking for internal feathering or fissures. Stones that are clean to the naked eye are considered good quality.
- 3
  Inspect the garnet under a 10-to-1 ratio magnification. Reference the GIA rating terms in Step 1 to assess the stone.

Gemology