Garnets are a group of silicate minerals, Garnet forms when a sedimentary rock with high aluminum content, such as shale, is metamorphosed. Garnet has a hardness of 6.5 to 7.5 on the Mohs scale. This piece of Mahenge Garnet rough from Tanzania, Africa weighs 6.33 cts., measures 11x9X7 mm. and has some minor veils. Available at New Era Gems.