This stone is found in various colors, grass-green, pale-green, light-blue, greenish-blue, greenish-yellow, yellow, and sometimes pink.
The most important of these colors is the grass-green, which forms a separate division of the beryl family, and is known as the emerald.
Emerald.
The emerald or green beryl is one of the most highly prized of the gem stones. Its magnificent color has rightly been compared to the color of the fresh grass in spring, and in brilliancy this stone far exceeds all other green gems, excepting only the very rare green corundum or green sapphire.
The emerald is said to be very soft when first withdrawn from the mine, but it hardens by exposure to the air.
A perfect emerald of fair size is a rarity, so that the saying “an emerald without a flaw” has passed into a proverb.
This stone is so light, compared to a diamond or sapphire, that a carat emerald will be very much larger than either of the above stones.
| Silica | 68.50 |
| Alumina | 15.75 |
| Glucina | 12.50 |
| Peroxide of iron | 1. |
| Lime | 0.25 |
| Oxide of chrome | 0.30 |
| And traces of magnesia, | |
| of lime, and of soda. |
The vivid green color of the emerald is supposed to come from the oxide of chrome, as the other beryls do not contain chrome.