Johnson and Warren — Geology of Rhode Island. 13 



grains up to individuals 2 or 3 ram thick by 2 om square. The 

 average, and likewise the most common size, is perhaps about 

 2 mm thick by 1 CG0 square. By the very general segregation of two 

 or more of the feldspar crystals together, the rock assumes 

 what may be termed a " cumulophyric " texture.* A more or 

 less distinct parallel (flnidal) arrangement of the feldspars may 

 be noted in portions of the ledge and in individual specimens, 

 but no single direction of orientation has been made out in the 

 rock as a whole. The direction, therefore, which any particular 

 surface of the ledge or of a hand-specimen makes with the local 

 direction of flow, taken in connection with the tabular habit of 

 the feldspar, determines very often the apparent abundance or 

 paucity of the feldspar phenocrysts on the surface in question. 

 In some of the bowlders found on the edge of the swamp to 

 the west and believed to have been loose bowlders taken from 

 the old talus or drift about the hill, the feldspars have a very 

 marked parallel arrangement. While a careful study of the out- 

 crop shows that the feldspar is more abundant in some places 

 than others, it seems highly probable if not certain that the 

 feldspar had a fairly uniform distribution in the rock as a 

 whole. 



Although the characteristic tabular habit of plagioclase is 

 strongly developed it is rather surprising to note, particularly 

 in thin section, that the crystal outlines are always rounded 

 toward the minerals of the enclosing groundmass. The 

 rounded ends may be sometimes seen buried in an olivine or 

 ilmenite-magnetitef grain and actual inclusion of small feldspar 

 anhedrons by the olivine are not uncommon. On the other hand, 

 the margins of the feldspars are indented by the groundmass 

 grains, and as noted by Wadsworth, small " tongues " of feld- 

 spar run out into the groundmass. Occasional irregular pieces 

 of feldspar may also be seen in the interstices between the 

 olivine and ore. Olivine and ore grains are also imbedded in the 

 feldspar, but so far as observed, these are always situated either 

 on the contacts between individuals, along fracture lines, 

 or in fractured portions of the feldspar near the border. 

 Their mode of occurrence has led to the conclusion that they 

 have reached their present positions not through crystal lographie 

 inclusion but by mechanical means. The feldspar crystals are 

 bent, broken, the parts deorientated and recemented ; again 

 they are jammed into other feldspars as well as into the surround- 

 ing groundmass. Everywhere there is abundant evidence of 

 movement. 



*See The Texture of Igneous Eocks, Jour. Geol., vol. xiv, No. 8. 1906. 

 f The ilmenite-magnetite will for bi*evity hereafter be generally referred 

 to simply as ore. 



