CONTENTS. 



21 



Chapter IX. — Kocks — Continued. Page. 

 Sedimentary rocks — Continued. 



Nonfragmental class — Continued. 



Sulphate order 788 



Gypsum and anhydrite family i 788 



Chloride order _ 789 



Rock-salt family 789 



Carbonate order 791 



Calcium-magnesium carbonate family and metamorphosed equivalents -. . 791 



Limestones 791 



Source of material of limestones 791 



Organic precipitates 792 



Chemical precipitates 793 



Springs and streams 793 



Inland seas with no outlets 793 



Possible chemical precipitates in the ocean or jn seas con- 

 nected with the ocean 793 



Metamorphism of organic and chemical calcium carbonate deposits. . 795 



Dolomite - 798 



Origin of dolomite 798 



Dolomite due to replacement of calcium by magnesium. 798 



Conclusion 802 



How and why dolomitization occurs -' 802 



Dolomitization before limestone emerges from the sea 802 



Dolomitization after limestone emerges from the sea 804 



Marble 808 



Cherty limestones, cherty dolomites, and cherty marbles 816 



Silicated marbles 820 



Silicate rocks 822 



General statements 823 



Iron-bearing carbonate family and metamorphosed equivalents 823 



Siderite, ankerite, and parankerite 823 



Origin of siderite, ankerite, and parankerite 824 



Ferruginous shales, ferruginous cherts, and jaspilites 829 



Ferruginous shales ' 830 



Ferruginous cherts 830 



Jaspilites 831 



Actinolitic and griineritic marbles 833 



Actinolite-magnetite-quartz rocks and grunerite-magnetite-quartz rocks. 834 



General statements 841 



Oxide order 842 



Iron-oxide family G42 



Limonite 842 



Hematite 843 



Magnetite 845 



