Garnet skarn from Marmora, Ontario, Canada. Comes with certificate of authenticity. Collectible minerals. Type: contact metamorphic rocks. Stone type: Skarn to garnet. Dominant color: multicolored. Origin: Canada. Average weight (Carats): 20.5 carats. Dimensions (mm): 16 x 15 x 14 mm. Ref. : SKU031043. Rocks formed by the transformation of existing rocks under pressure, heat, and chemical fluids, such as marble and shale.