4 CONTENTS AND ILLTISTRATIONS. 
Corundum-bearing rocks in the United States — Continued. Page. 
Corundum in metamorphic rocks — Continued. 
In metamorphosed zone between harzburgite and gneiss 53 
In mica-schist . _ _ _ 54 
In quartz-schist . _ . 55 
In amphibole-schist 57 
In chlorite-schist . 59 
In crystalline limestone 60 
Corundum in alluvial deposits . 61 
Emery in undetermined association 61 
Foreign occurrences of corundum 62 
Corundum in foreign igneous rocks 62 
In kyschtymite 62 
In diorite 62 
In tonalite 63 
In gabbro 63 
In nepheline-syenite and syenite-pegmatite . 63 
In quartz-porphyry 64 
In trachyte 64 
In basalt . _ 64 
In contact zones and inclusions 64 
Corundum in foreign metamorphic rocks _ _ 65 
Corundum-schists and porphyroids . _ _ 65 
Corundum in graphite 65 
Minerals associated with, and alteration products of, corundum 66 
List of associated minerals 69 
Origin of corundum 71 
Artificial production of corundum 71 
Origin of corundum in igneous rocks 76 
Origin in peridotite _ _ . 76 
Review of literature 76 
Relations of corundum to peridotite 79 
Theory of origin in peridotite 81 
Summary 86 
Origin >of emery in amphibolite at Chester, Mass 93 
Origin of corundum in norite 93 
Origin of corundum in plumasite 94 
Origin of corundum in monchiquite 94 
Origin of corundum in metamorphic rocks 95 
Origin in amphibole-schist _ 95 
Origin in quartz-schist 96 
Distribution of corundum in the United States 97 
Sapphire or gem corundum 97 
Ruby 97 
North Carolina 98 
Georgia 105 
Montana 105 
Sapphire 105 
North Carolina . 105 
Montana 106 
Idaho 116 
Corundum . . 116 
North Carolina 116 
Georgia 127 
South Carolina 130 
