The cleavage surfaces therefore exhibit a metallic sheen or schiller, which is even more pronounced in hypersthene than in bronzite.[2] The color of bronzite is green or brown; its specific gravity is about 3.3–3.4, varying with the amount of iron present.[2] The refractive indices and optic angle increase with iron content. The enstatite endmember has a positive optic sign, whereas bronzite and hypersthene both show a negative optic sign.[2]