Gemstone usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons. Gemstones are classified into different "groups", "species", and "varieties". For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow) and morganite (pink), which are all varieties of the mineral species beryl. Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture and luster. They may exhibit pleochroism or double refraction. They may have luminescence
Varieties of Chinese Varieties of Chinese Chinese, also known as Sinitic, is a branch of the Sino-Tibetan language family consisting of hundreds of local language varieties, many of which are not mutually intelligible. The differences are similar to those within the Romance languages, with variation particularly strong in the more mountainous southeast. These varieties, often called "dialects", have been classified into seven to ten groups, the largest being Mandarin (e.g. Beijing dialect), Wu (e.g. Shanghainese), Min (e.g. Hokkien), and Yue (e.g. Cantonese). Chinese varieties differ most in their phonology, and to a lesser extent in vocabulary and syntax. Southern varieties tend to have