free download PNG images :Emerald

Jadeite is a kind of gem. It is the green of various mineral beryl (be3al2 (SiO3) 6), which is dyed green by trace chromium and sometimes vanadium. The Mohs hardness of beryl is 7.5-8. Most emeralds are included, so their toughness (fracture resistance) is classified as generally poor. Emerald is a kind of cyclosilicate.

Like all colored gemstones, emeralds are graded using four basic parameters (four C's identified): color, clarity, cut and carat weight. Before the 20th century, jewelers used the word "water" to mean "gem of high quality water", to express the combination of two qualities: color and purity. Generally, in the classification of colored gemstones, color is the most important standard so far. However, in the emerald grading, clarity is considered to follow. A good emerald must not only have a pure Turquoise hue as described below, but also have a high degree of transparency to be considered a top gemstone.

In the 1960s, the U.S. jewelry industry changed the definition of emerald to include green vanadium beryl. As a result, vanadium emeralds were not purchased as emeralds in the United States and Europe. In the United States, the difference between traditional emerald and new vanadium species is usually reflected in the use of terms such as "COLOMBIAN EMERALD".