REPORT OF THE STATE GEOLOGIST. lvii 



ing hard under water. Portland cements are of similar character, but 

 are made by artificially mixing the limestone and clays in the proper 

 proportion. 



Materials for both characters of cement exist in abundance within 

 the State. The limestones of certain beds of the Cretaceous are argil- 

 laceous enough to make cement when properly calcined and ground, 

 and the same properties are claimed for some of those found in the 

 Tertiary, but our tests have so far failed to bear out the claim. Some 

 of the limestones belonging to the Clear Fork Beds of the Permian 

 might answer if the percentage of magnesia was not too great. 



The materials for Portland cement are, however, more abundant, and 

 the product of so much better quality as to render the natural cement 

 a matter of comparatively small importance. The Austin Chalk is 

 rather widespread in its distribution and adjacent to clays of almost any 

 required grade. 



The entire practicability of the manufacture of Portland cement has 

 been shown by the two factories which have undertaken it, one at San 

 Antonio, the other at Austin. The former supplied much of the cement 

 used in the erection of the present Capitol building, and as the reports 

 of it by G-en. Gilmore show, it was of very excellent quality. 



The works at Austin are now under way, and it is proposed to in- 

 crease their capacity. 



PLASTER PARIS. 



Plaster Paris is produced from gypsum by driving out the percent- 

 age of water which is chemically combined with it. Its manufacture 

 on any desired scale is entirely practicable in the Permian region of 

 Texas, where many beds of gypsum of great purity occur. 



SANDS FOR MORTAR, ETC. 



Sand for mortar, plaster, etc., is found in many places. The Creta- 

 ceous is perhaps the area in which it is scarcest, and it can be brought 

 in from either side. The locations will be more fully discussed in the 

 descriptions of counties. 



METALS AND OEES. 



IRON. 



Probably the most important of our ore deposits are those of iron, 

 which io various forms are found in many parts of the State. 



