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
Shades of green of its unofficial mascot, the Dartmouth Indian, in 1974. Dartmouth green and white are the main colors of Lithuanian basketball club Žalgiris Kaunas. "Emerald", also called "emerald green", is a tone of green that is particularly light and bright, with a faint bluish cast. The name derives from the typical appearance of the gemstone emerald. The first recorded use of "emerald" as a color name in English was in 1598. Ireland is sometimes referred to as the "Emerald Isle" due to its lush greenery. The May birthstone is emerald. Seattle is sometimes referred to as the "Emerald City", because its