xlii REPORT OF THE STATE GEOLOGIST. 



. THE BASAL CLAYS. 



Between the Timber Belt beds and the underlying Cretaceous strata 

 there are great beds of stratified clays with little sand, which are called 

 the Basal or Wills Point clays. The country underlaid by them is the 

 extreme eastern extension of the Central Texas prairies, interspersed 

 with belts and groves of post oak, black jack, and hickory, and does 

 not exceed ten miles in width, in places, though it extends from Red 

 River to beyond the Colorado. 



The clays are of various colors, stiff, laminated, with some interbed- 

 ded seams of sands, and contain concretions of grey, non-fossiliferous 

 limestone, and frequently fine crystals of gypsum. They are especially 

 characterized by small segregations or concretions of calcareous matter 

 of cauliflower- like form. 



The soils vary from clay to clay loams, and as they contain much 

 lime they are dark colored. The subsoils are yellow or grey clays with 

 a little sand. The soils are very rich and produce as well as many of 

 the soils of the black prairies, from the erosion of whose materials they 

 were originally derived. These are the lowest beds of the Tertiary 

 formation in Texas as far as has been determined, and seem to be en- 

 tirely lacking on the Rio Grande. In their northeastern portion they 

 contain deposits of iron ore which are of considerable value and which 

 will be spoken of under that heading. 



Iron Ores of the Tertiary. — The workable ores of the iron re- 

 gion of Eastern Texas, the value of which can hardly be overestimated, 

 occur in the areas covered by the Basal clays and Timber Belt beds, 

 and are either limonites or clay ironstones, the former being by far 

 the most important. Limonite is a compound of iron and ogygen com- 

 bined with a certain percentage of water. When perfectly pure it 

 contains: 



Water 14.40 



Iron 59 92 



Oxygen 25 . 68 



100.00 



It is usually associated with clay or sand, and often contains small 

 amounts of such impurities as phosphorus and sulphur. It is not often, 

 however, that these impurities are present in the ore of this region in 

 such quantities as to seriously interfere with the working of the ore. 

 The clay ironstone or carbonate of iron, which has been reported as 



