Loose Gemstones | Gem Art | Gem Stone Information



	THE PEARL

	a rough, warty exterior. The supply is small and uncertain. Another rare species is the butterfly (Plagiola securis). It is a small, flat, thick shell of fine color, and the valves are butterfly in shape with a reddish-brown epidermis striped by darker radiating lines. It is abundant only in the Illinois and Ohio rivers. The hatchet-back, hackle-back, or heel-splitter (Symphynota complanata), is a large black mussel having a thin sharp-edged shell, one valve-edge projecting. It yields few pearls though fine specimens are occasionally found in this variety. The blue-point (Quadrula undulata) has a large, thick shell, with ridges on the exterior, curving round the umbones and extending to the edge. Like the black-edge meleagrina, the nacre at the edge is discolored. In this case by a bluish or purplish tint. Some idea of the enormous quantities of mussels contained in some of these beds in our western rivers may be gained from the reports of the fisheries in the first years of their discovery. Ten thousand tons of shells were 268