Boulder Matrix Opal. Mohs Hardness: 5.5-6.5 Found in Australia History: Opal is a semi-transparent solidified mineral composed of silicon and water. Boulder opal refers to a clear water opal with brilliant color play and a distinctive dark chocolate brown ironstone matrix.
9.58 ct Fancy (20 x 22 mm) (Un-Heated) Australia Boulder Matrix Opal Gemstone
9.58 ct Marvelous Fancy (20 x 22 mm) 100% Natural (Un-Heated) Australia Boulder Matrix Opal Loose Gemstone. Boulder Matrix Opal. Mohs Hardness: 5.5-6.5 Found in Australia History: Opal is a semi-transparent solidified mineral composed of silicon and water.