66 GULF TERTIARY OF TEXAS. 



in description, they have been grouped under three different headings, and 

 will be treated separately. 



1. Brown Laminated Ores. 



2. Nodular or Geode Ores. 



3. Conglomerate Ores. 



1. BROWN LAMINATED ORES. 



These ores are extensively developed south of the Sabine River, especially 

 in the counties of Cherokee, Anderson, Smith, Rusk, and probably in Harri- 

 son, Panola, Nacogdoches, and Shelby, though this latter region has not been 

 examined. The extension of this belt to the southwest across the Trinity 

 River also remains to be examined. 



The ore is a brown hematite of a rich chestnut color, and often of a highly 

 resinous lustre. In structure it varies from a compact, massive variety show- 

 ing no structure, to a highly laminated form, the laminae varying from one- 

 sixteenth inch to one-quarter inch thick, frequently separated by hollow spaces, 

 and sometimes containing thin seams of gray clay. These often give it a 

 buff color and a crumbly nature, and hence the name often applied to it of 

 "Buff Crumbly Ore." The laminae frequently show a black glossy surface, 

 though the interior is always the characteristic rich chestnut brown color. 



The table of analyses which have been made at the Survey Laboratory is 

 given beyond. The ore occurs in a horizontal bed from one to three feet 

 thick, and averages between eighteen inches and two feet in thickness. It 

 is flat on top, but is bulging and mammillary below and lies at or near the 

 summits of the highest hills in the region In fact, it is to this protecting 

 cap of hard material that the hills owe their existence, as it has saved the 

 underlying soft strata from the effects of erosion, which otherwise would 

 quickly have lowered them to the level of the surrounding rolling country. 

 The iron ore bed is directly underlaid by a deposit varying from thirty to 

 forty feet thick of a soft yellow indurated glauconite (greensand). This 

 bed is sometimes hardened into a soft rock, easily cut with a saw or 

 axe, and locally used as a building stone. The interior of the bed, how- 

 ever, where it has not been exposed to the atmosphere, retains the dark 

 green color of the unaltered greensand. It contains considerable iron 

 pyrites and numerous casts of fossils of the Claiborne epoch, and repre- 

 sents the northeasterly extension of the Smithville Beds of the Colorado 

 River. This bed in turn is underlaid by a great series of sands and clays, 

 for a description of which see Timber Belt Beds. Sometimes thin seams 

 of iron ore are found in the greensand below the main ore bed, but they are 

 small and rarely of value. At times they lie horizontally, and at others 

 occupy joint cracks. The main ore bed is usually directly overlaid by a thin 



