216	GEMS AND PRECIOUS STONES IN THE
	A hundred pearls have been found in a single shell; but as a rule these have little or no value. Very curious nacreous groups made of many small pieces are at times found attached to the hinge, but these are generally without sufficient lustre to be of value, and are rarely collected. These groups are caused by the conglomeration of many small ones cemented by a deposit of nacre, and are often half an inch across. The white and the pink pearls are exceedingly beautiful, and the finest, owing to their delicate sheen or layers, are at times more lustrous than even the best oriental pearls. This lustre is increased by their greater transparency, and a really fine white, pink, yellow, or iridescent pearl is often found quite translucent. In color, the Unio pearls present an extended series of shades from dead opaque white, having but little value, through various tints of pink, yellow, and salmon, passing through a more decided form of these colors, or a faint purple, into a bright red, so closely resembling a drop of molten copper as almost to deceive the eye. Some are very light green and brown, others rose color, and still others are pale steel-blue or russet and purplish brown. In addition to their color and lustre, they are beautifully iri­descent. They are found in many odd and remarkable shapes. (See Illustration.) Elongated fish forms found near the hinge of the shell, and called hinge baroque pearls, are abundant. Others, with but a slight addition of gold and enamel, seem to represent human and animal heads, bat and bird wings, and similar objects. Mallet-shaped pearls are found with fine color and lustre at each end, though generally with opaque sides; also grouped or bunched masses of the pearly nacre, made up of from one to over one hundred distinct pearls in fanciful shapes, are of occasional occurrence. Feather-like forms with curiously raised points, and an odd, rounded variety with raised, pitted markings, are quite abundant. A pearl was mounted in this country that strikingly resembled the bust of Michael Angelo, and a number of unique designs have been made of baroques, similar to those mounted by Dinglinger and exhibited in the Green Vaults at Dresden. Although the pearls used here have not been as large as those shown in Dresden, greater taste has been employed in mounting them. The variety of the