. Bulletin of the Geological Society of America. Geology; Geology -- United States. SECONDARY MINKRALS AND I:T( HIXGS 277 still unaltered, but their surfaces are deeply etched, pits and narrow grooves cutting into the surfaces 3 or 5 and even to 15 mm. (see figure 11. specimen TT616, and figure 12, specimen 88435). These markings \ary in shape and size from semicircular grooves, which have been well chai- acterized as lunar crater forms by ({. P. ^Ferrill,^' to straight channels not unlike the marks left bv an enufraver's tools. The distribution of the various markings, both it-giihii' and ii'
. Bulletin of the Geological Society of America. Geology; Geology -- United States. SECONDARY MINKRALS AND I:T( HIXGS 277 still unaltered, but their surfaces are deeply etched, pits and narrow grooves cutting into the surfaces 3 or 5 and even to 15 mm. (see figure 11. specimen TT616, and figure 12, specimen 88435). These markings \ary in shape and size from semicircular grooves, which have been well chai- acterized as lunar crater forms by ({. P. ^Ferrill,^' to straight channels not unlike the marks left bv an enufraver's tools. The distribution of the various markings, both it-giihii' and ii'i-i-giilai'. follows no discerniblr oi'ilcr; and the (piestion of the mode of foi'niation of such remarkable etch phenomena is of interest esjiecially heeause of the siniilnritv (d' these. Fn;i Ki: 11.—Ijiciiril Snrftuc of (ihshlimi (llass, Diiihlaiil h- in ('Inn itrter Specimen 77(510. Two-thirds natural size markings to those which are found on the moldavites of Bohemia, which have lieen described in great detail l)y F. E. Sness,^* who considers them to he of origin. In the present case the origin of the etch (igiircs is clearly shown by the records contained in the present suite of specimens. The following facts have a direct bearing on the problem: (T ) The etching is evidently the work of hot and iirobablv alkaline solutions. This is inferred from 13 I'roc. r. S. National Miisciini. vol. t(i. |.. \Sn. ".Jahrlj. (1. K. K. (». I'miii. pii. i'.»:;-;{ Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York, etc. ] The Society
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