ISBN: 9781130308440

RareBooksClub. Paperback. New. This item is printed on demand. Paperback. 192 pages. Dimensions: 9.7in. x 7.4in. x 0.4in.This historic book may have numerous typos and missing text. Pur… More...

RareBooksClub. Paperback. New. This item is printed on demand. Paperback. 192 pages. Dimensions: 9.7in. x 7.4in. x 0.4in.This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 Excerpt: . . . terminated crystals, but no crjptocrystalline or amorphous silica could be detected. Many of these geodes, as shown in plate 17, figure 2. are deeply etched upon one or both sides, not only the outer opaque shell being removed, but portions of the translucent interior. A part of this etching was probably accomplished by the solvent which removed the limestone, as one specimen at least was found embedded in the residual clay between two layers of limestone, evidently not far removed from its original position in the rock. In most cases, however, the solution was evidently effected after the geodes reached the SILICIOUS GEODES AND ETCHED CONGLOMERATE. F1gure 1. -etched Conglomerate Pebbles From Cl1fty Creer, Wh1te Co. , Tennessee (natural size) ETCHED CONGLOMERATE PEBBLES FROM NUTTALL, WEST VIRGINIA (atxnlt natural size) 215 surface by the weathering of the enclosing rock, and is confined largely to their exposed upper sides. From its microscopic structure, the silica of which these geodes are composed would appear to be but little more liable to solution than vein quartz or quartzite. Minute quantities of amorphous silica may, however, be present and by their solution facilitate the removal of the crystalline grains by solution or otherwise; hence less importance is attached to the solution of these geodes than to the etching of conglomerate pebbles composed of various forms of silica which has been observed at several rather widely separated points in the south. ETCHED CONGLOMERATE FROM NUTTALL, WEST VIRGINIA. The first case to be described is one observed by Mr Campbell at Nuttall, West Virginia. The conglomerate in question, which belongs to the coal measures, is composed of rather coarse quartz sand with slightly yellowish cement, in which are embedded. . . This item ships from La Vergne,TN., RareBooksClub<