CONTENTS. i 



Classification of mineral lands — Continued. 

 Coal lands — Continued. 



Field work on coal lands — Continued. Page. 



Attitude and depth of tbe coal 105 



Quality of the coal 105 



Preparation of material 108 



Procedure in classification and valuation 108 



Progress in classification and valuation 111 



Oil and gas lands :_ ill 



Occurrence of oil and gas 111 



Classification of oil and gas land 117 



Phosphate lands 123 



Use of phosphate 123 



Lands containing phosphate 124 



Phosphate reserves 125 



Florida reserves 125 



Western reserves 125 



Summary of phosphate situation 127 



Classification of phosphate lands 128 



Factors involved 128 



Principles controlling classification 129 



Regulations 1.30 



Progress in classification 131 



Lands bearing potash and related salines 134 



Geologic occurrence of the deposits 134 



Classification of potash-bearing lands 137 



Miscellaneous nonmetalliferous mineral lands 138 



Metalliferous mineral lands 142 



Purpose of classification 142 



Methods of classification 145 



Agencies employed Kfi 



Problems involved 145 



Preliminary procedure 14fi 



Field work 146 



Location and topography 146 



Investigation of placer deposits 147 



Geologic relations 147 



Testing 147 



Testimony of miners 147 



t Investigation of lode deposits 148 



Kinds of evidence available 148 



General geology 148 



Country rock ■ 149 



Intrusions and metamorphism 150 



Structure 151 



Outcrops and float of lodes 151 



Prospects and mines 154 



Samples and assays 154 



History of the region , 155 



By-products of mineral-land classification 155 



Value of collateral information obtained 155 



Data of direct interest to the public at large 156 



Data relating to prospecting and mining 157 



Scientific data 158 



