The yellow variety of sapphire is quite common, and exhibits many of the finest shades of yellow; but they are generally very faint in tint and often like the lemon in hue. They are exceedingly liable to imperfections, and especially to that opalescence which so often disfigures the red sapphire. Fine specimens, therefore, possessing transparency and beauty of color, are rare gems. But when it does occur in perfection, it forms a magnificent gem, which is only surpassed by the yellow diamond and zircon. Its rich golden hues, with soft and satin-like flashes, are far superior to the Brazilian topaz. The Museum of Natural History in Paris possesses one of the finest yellow sapphires known. It is a wonderfully lustrous gem of fine color, and measures nearly an inch in length by half an inch in breadth. There is also in the same cabinet a strange gem which was once placed among the crown jewels of France. It was mentioned in the famous inventory of 1791, as a singular corundum of 19²⁄₁₆ karats weight, and of 6,000 francs value. It had been polished in the form of an elongated oval, and exhibited the remarkable appearance of being deep-blue at the extremities and yellow in the centre. This singular distribution of color is not often seen in fine specimens, although it is frequently met with among the inferior. We have also had the pleasure of examining another large gem, cut into the form of a brilliant, whose diagonal corners were blue and yellow, and yet, such was its play of dichroism, that light reflected through these two colors produced but a faint tinge of green. This double arrangement of coloring is sometimes seen with blue and red sapphires, or yellow, blue, and white; but we have learned of but one fine gem displaying the red and yellow. Several of the transparent crystals from North Carolina exhibit the two hues in the same crystal; and we have seen one that was actually red, yellow, white, and blue. But the specimen was not sufficiently perfect to form a gem. Sometimes the yellow hues are of a greenish cast, and then they resemble the finest of the golden chrysoberyls, or they may approach the more verdant shade of the peridot. It is said by the antiquaries that none of the collections of ancient Greek and Roman engraved gems possess a single specimen in yellow sapphire. This singular absence may be partly accounted for by its rarity in perfection, and also from its liability to appear pale when set in gold.