Читать книгу The Book of the Pearl. The history, art, science, and industry of the queen of gems онлайн

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The buckhorn (Tritigonia verrucosa) is very long and narrow; on the dark brown exterior it is rough, as is the horn from which it takes its name, while the interior shows a beautiful display of colors. This is not found in beds, but lies scattered among other species. It sells at a relatively high price—usually in excess of $20 per ton—for button manufacture.

Another species is the butterfly (Plagiola securis), which is very prettily marked on the outside with faintly colored dotted stripes of varying length. Over a background of dark yellow run black stripes to the outer edge of the shell, with dark dots between the stripes. The shell is small and thick, and like the sand shell and the buckhorn, is found in small quantities. Owing to the beauty and permanency of its luster, this shell is in demand for button manufacture, and its pearls are often very beautiful.

Other well-known species are the pancake (Lampsilis alatus), the maple-leaf (Quadrula wardi), and hackle-back (Symphynota complanata). On the Atlantic seaboard, the principal species in which pearls have been found are Unio complanata; the Alasmodon arcuata, which has hinge teeth, and a species of Anodon. Pearls from the Unio complanata are usually smaller but more lustrous than those from either of the other species.