274 REPORT OF NATIONAL MUSEUM, 1899. 



A lithographic stone is described in the State survey reports of 

 Texas as occurring at the base of the Carboniferous formations near 

 Sulphur Springs, west of Lampasas, on the Colorado River, and to be 

 traceable by its outcrops for a distance of several miles, the most 

 favorable showing being near San Saba. The texture of the stone is 

 good; but as it is filled with fine reticulating veins of calcite (Specimen 

 No. 70671, U.S.N.M.), and as moreover the lithographic layer itself is 

 only some 6 or 8 inches in thickness, it is obvious that little can be 

 expected from this source. The Texas Lithographic Stone Company, 

 with headquarters at Burnet, have used the stone, it is said, in con- 

 siderable quantities. A stone claiming many points of excellence has 

 for some years been known to exist in the Wasatch range within a 

 few miles of Salt Lake City, and several companies are or have been 

 engaged in its exploitation. 



Very encouraging reports of beds examined by men whose opinions 

 should be conservative, come from Canadian sources, and it is possible 

 a considerable industry may yet be here developed, though little is 

 being done at present. The descriptions as given in the geological 

 reports are as follows: l 



The lithographic stones of the townships of Madoc and Marmora and of the 

 counties of Peterboro and Bruce have been examined and practically tested by 

 lithographers, and in several cases pronounced of good quality; they have also 

 obtained medals at various exhibitions. They were obtained from the surface in 

 small quarries, and possibly when the quarries are more developed better stones, 

 free from "specks" of quartz and calcite, will be available in large slabs. 



It should be stated that in actual use the principal demand is for 

 stones some 22 or 28 by 40 inches; the largest ones practically used 

 are some 40 by 60 inches and 3 to 3i inches thick. As the better 

 grades bring as high as 22 cents a pound, it will be readily perceived 

 that the field for exploration is one offering considerable inducement. 



2. DOLOMITE. 



This is a carbonate of calcium and magnesium (Ca, Mg), CO 3 , = 

 calcium carbonate 54.35 per cent, magnesium carbonate 45.65 per 

 cent. Hardness 3.5 to 4; specific gravity, 2.8 to 2.9; colors when pure, 

 white, but often red, green, brown, gray, or black from impurities. 

 (Specimen No. 82167, attached crystals on limestone from Joplin, Mis- 

 souri.) Dolomite, like calcite, occurs in massive beds or strata either 

 compact (Specimen No. 37795, U.S.N.M.) or coarsely crystalline, and 

 is to the eye alone often indistinguishable from that mineral. Like 

 limestone, the dolomites occur in massive forms suitable for building 

 purposes, or in some cases as marble. (Specimen No. 25075, U.S.N.M.) 

 From the limestone they may be distinguished by their increased hard- 

 ness and being insoluble in cold dilute hydrochloric acids. The dolo- 

 mites, like the limestones, are sedimentary rocks, though it is doubtful 



1 Geology of Canada, 1863. 



