a genus of precious stones belonging to the order of siliceous earths. The word is derived, according to some, from the French émaurande, and that from the Latin smaragdus, signifying the same thing; by others it is said to be derived from the Italian smaragdo, or the Arabian somorrad. According to Cronstedt the emerald is the softest of all the precious stones, though other naturalists place it the next after the diamond in this respect. It is perhaps the most beautiful of all the gems, and, according to Wallerius, when heated in the fire, changes its colour to a deep blue, and becomes phosphorescent; but recovers its green colour when cold. When pulverized it has a white appearance, and, with borax, melts to a very thin and colourless glass. It becomes electric by being rubbed, and some have the property of the tourmalin, viz. of being electrified by heat, and in that state attracting ashes or other light substances; though the emeralds are less powerful than the tourmalin, and after having attracted the ashes, they retain them without any signs of repulsion.

Pliny mentions twelve different kinds of these precious stones; though it appears, from the vast size of some of them, that they must have been only certain kinds of green spar, or other green stone, which at that time Emeralds ready cut, or polished and not cut, being of Emerald's good stone, and a fine colour, are worth—

| Carats | Value | |--------|-------| | One | 10 | | Two | 7 | | Three | 5 | | Four | 10 | | Five | 10 | | Six | 10 | | Seven | 15 | | Eight | 19 | | Nine | 23 | | Ten | 33 |

To counterfeit Emeralds: Take of natural crystal, four ounces; of red lead, four ounces; verdigris, forty-eight grains; crocus martis, prepared with vinegar, eight grains: let the whole be finely pulverized and fitted; put this into a crucible, leaving one inch empty: lute it well, and put it into a potter's furnace, and let it stand there as long as they do their pots. When cold, break the crucible; and you will find a matter of a fine emerald colour, which, after it is cut and set in gold, will surpass in beauty an oriental emerald.