122 Transactions of the Academy of Science of St. Louts 
The tuff is fine-grained and firmly cemented, generally pink 
or buff in color, with some green varieties, and some contains 
concretions, which appear to be made up of siderite. Though 
the tuff is usually stratified and sometimes finely laminated, the 
agglomerate is never stratified. 
Sedimentary rocks. There are no undoubted pre-Cambrian 
sedimentary rocks in Missouri, although the pyroclastics were 
once considered to be metamorphosed sediments. Dake(11) 
mentions a deposit near Redmondville which might be a conglom- 
erate although it is probably an agglomerate. Boulders of quartz- 
ite are found in considerable number in the Tom Sauk Moun- 
tain area, but they may be merely a phase of the Lamotte sand- 
stone. Drill-holes in the more northern parts of the state pass 
through a considerable thickness of pink quartzite lying above 
the igneous rocks which may be metamorphosed sandstone of 
pre-Cambrian age. The drill-hole at Raytown(38) in Jackson 
County, penetrates a black mica schist which might be a meta- 
morphosed shale. A drill-hole in Jasper County, at Carthage 
(38), is reported to have passed through felsite and then en- 
tered limestone. 
Relative ages of pre-Cambrian rocks. The following table 
shows a suggested sequence of some pre-Cambrian events, the 
latest being listed first. There are no doubt many intrusions 
not included, and some of the events may not be in their right 
order, for the present work would have to be supplemented by 
detailed petrographic studies to more definitely determine the 
age relations of the various intrusions. 
SEQUENCE OF PrE-CAMBRIAN EVENTS 
Mineralization—Silver Mine and region southwest of Coldwater. 
Intrusion of basic dikes—in granite near Coldwater. 
Intrusion of gray granite—Ste. Genevieve County and Mine 
La Motte quadrangle. 
Intrusion of Graniteville granite—at Graniteville, Cornwall, 
southwest of Coldwater, and within main granite area. 
Intrusion of black felsite—at Cornwall. 
