MARBLES. 



MR. GEO. D. MERRILL, 

 Head Curator, Department of Geology, U. S. National Museum. 



THE origin of tlie name marble, 

 like that of many another name 

 now in common use, is some- 

 what obscure. By many au- 

 thorities the word is supposed to have 

 been somehow connected with the 

 Greek word meaning " sparkle." How- 

 ever this may be, a sparkling appear- 

 ance is by no means universal among 

 marbles, but is limited to those which, 

 like the white statuary or other crystal- 

 line varieties, have a granular structure, 

 •the sparkling itself being due to the 

 reflection of light from the smooth 

 surfaces of the constituent minerals. 

 As used to-day, the word marble is 

 made to include any lime rock of such 

 color and hardness as to make it desir- 

 able for ornamental, or even the higher 

 grades of building work. Stones of 

 precisely the same composition and 

 origin, which are not of the desired 

 color, are classed simply as limestones. 

 Accepting the definition given above, 

 it follows, then, that with a few excep- 

 tions, to be noted later, marbles are 

 but hardened and otherwise changed 

 beds of marine sands and muds, con- 

 taining, it may be, still recognizable 

 fragments of the corals and mollusks 

 of which they were originally com- 

 posed. But inasmuch as these muds 

 were rarely of pure carbonate of lime, 

 but were contaminated with matter 

 from seaweeds and animal remains, or 

 by iron compounds, so the resultant 

 marble is not always white, but, if con- 

 taining matter from plants or animals, 

 gray, blue gray, or even black; and if 

 containing iron, buff, pink, or red. If 

 the change in form of the original 

 muds was just sufficient to produce 

 crystallization, we may have a marble 

 full of fossil remains which may be of 

 a white or pink color, standing out in 

 fine contrast with the darker ground. 

 If, on the other hand, the change was 

 complete, we may ha\e a marble of 

 small granules, pure white in color, and 

 of a texture like loaf sugar, such as to 

 render it suitable for statuar)' purposes. 

 At one early period of the geologi- 



cal history of the North American con- 

 tinent, all that portion now occupied 

 by the Appalachian mountain system 

 was sea bottom, and on it was being 

 deposited not merely sediments washed 

 down from the land, but, in favorable 

 localities, deposits of lime, sand, and 

 mud. This deposit went on, on a gradu- 

 ally sinking floor, for long ages, until 

 the lowermost beds were buried under 

 thousands of feet of the later formed 

 materials. Then began the slow up- 

 lifting of the sea-bottom in the form 

 of long, parallel folds to form the 

 mountain ranges. During this uplift- 

 ing the lime sediments, which are the 

 only ones we need consider here, were 

 changed to marbles, and have since 

 been exposed and made available to 

 the quarriers through the wearing-down 

 action of rain and running streams. 

 So, then, a quarry is but an excavation 

 in the hardened mud formed on the 

 bottom of a ver}- ancient sea. 



In the Vermont marble region the 

 beds are highly inclined and of varying 

 colors. From the same quarry there 

 maybe produced pure white, gra), blue 

 gray, and greenish varieties, often vari- 

 ously veined and blotched owing to 

 the collection of their different impur- 

 ities along certain lines. Some of 

 these quarries have been worked a 

 depth of two hundred feet and more. 



Not all marble beds are upturned at 

 this steep angle, however, nor have 

 they been worked so deeply. In 

 Georgia, the quarries are often in hill- 

 sides, extending scarcely at all, if any, 

 below the surface of the ground. 

 Where opened in the valley bottoms 

 they have the form of huge rectangu- 

 lar pits, with perpendicular walls. In 

 Tennessee, many of the sediments 

 were so slightly changed that the fos- 

 sil remains are still easily recognized, 

 and the stone is of a pink or chocolate 

 red color, owing to the abundance of 

 iron 



The marbles are quarried mainly by 

 channeling machines, which cut out 

 the stone in blocks of any desired 



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