BUILDING STONES. 649 



grained and homogeneous in tint, others are variegated. The prevalent hue 

 is buff of several shades, but white, pink, and several shades of gray or blue 

 are occasional. The outcrops most suitable for working are those upon the 

 outer border of the district, where they have usually been least affected by 

 the more recent disturbances. Unlike the earlier marbles, they usually dip 

 at low angles, but' in selecting places to work it will be necessary to avoid 

 localities where the rock is much broken by joints. Such imperfections will 

 not improve with depth, and they may possibly increase. Many overlook the 

 sedimentary character of these beds and make excavations upon them like 

 shafts, as if they were veins, hoping that the joints may decrease as the sur- 

 face effects fade out below. But, aside from the ordinary textural results of 

 weathering, the tendency will be rather towards an increase of structural de- 

 fects as depth is gained. 



Samples of these marbles, in commercially available sizes, have been on 

 exhibition from different parts of the Silurian area. Burnet and San Saba 

 counties, from their proximity to railroads, have naturally made the best 

 showing, but the quality is not inferior in other counties. The Cretaceous 

 rocks cover the Silurian in the south, east, and west of the Central Mineral 

 Region so as to leave smaller tracts of the marbles exposed. In Burnet 

 County the workable area is limited, but considerably more extensive than 

 in any other county within the district, excepting San Saba. Mason County 

 comes next in amount of Silurian outcropping, but much of this is not of the 

 Hoover Division. Blanco County and McCulloch County are about equal in 

 Silurian, with probably more Hoover in the former. Kimble County had 

 some very good exposures, and Gillespie and Llano counties each have small 

 tracts. The pink and variegated marbles have the best natural exposures 

 north of the San Saba River in McCulloch County, the outcrops continuing 

 eastward in San Saba County. Prospecting has heretofore been most vigor- 

 ous in Hoover Valley, Burnet County, in various parts of San Saba County, 

 and on the Pedernales River, south of Cypress Mill, but in most instances the 

 material sought has been a " lithographic stone," with usually unfavorable re- 

 sults. As in many other cases of this kind, an industry of important propor- 

 tions is liable to be built up eventually with these marbles, but it will require 

 skill, experience, and detailed knowledge of the trade and the correct methods 

 of quarrying upon the part of those who are to make it a commercial success. 



C. LIMESTONES AND DOLOMITES. 



There are no general remarks to add this year to what was given in my 

 1889 Report upon the building material among the calcareous rocks other 

 than marbles. A review by geologic divisions, with reference to localities, 

 may be of service to those who seek such information. The oldest rocks con- 



