HC Set: 35mm Rainbow Clear Optical Calcite Crystal Natural Transparent Iceland Spar Double Refractive Clear Ice-Water Calcite Mineral Stone - Brazil + One Polished Yellow Jasper Cabochon from Africa You will receive exactly this Optical Calcite - 35mm x 28mm x 19mm / 1 3/8 x 1 1/8 x 3/4 Inches; 55g / 1.9 oz (see photo, stand and LED Light Base not included)! In additional, you will get one of the Yellow Jasper Cabochon similar to the one in the listing, the size and the color of the cabochon may slightly vary as well due to the fact that all minerals are different. Approximately Size: 10-30mm / 7/16-1 3/16 Inches; Approximately Weight: 15-40gr / 0.5-1.4oz. Optical Calcite is a transparent form of Calcite which is, chemically speaking, Calcium Carbonate. Commonly called Iceland Spar thanks to Icelands prolific output of this crystal, this form of Calcite is eye-catching for its perfect rhombohedral cleavage and demonstration of birefringence or double refraction. Calcite is the one of the most common minerals on earth. It occurs in a seemingly unlimited variety of shapes and colors. It constitutes a major portion of many of the earth's rocks. Calcite belongs to the calcite group of minerals, a group of related carbonates that are isomorphous with one another. Chemical Formula: CaCO3; Hardness: 3; Color Colorless; Light travels through Optical Calcite in two different directions and with two different velocities (one fast, one slow) which produce two different light rays! Observe this effect by placing a piece of paper with writing on it underneath Optical Calcite to see two images slightly offset from each other. (The above information is provided solely for informational purpose. Kindly note that all stones are offered for decorative purposes only. Please, handle your stones with great care, do not grind or crumble them, do not dip or add them into your food or drink, do not use any parts of them in any elixirs, potions, lotions etc. Always make sure you wash your hands before and after working with your crystals.)