404 DALE— CAMBRIAN MANGANESE DEPOSITS OF [April 25, 



indeterminate material (Fig. 25, Slide 244). Anisotropic minerals 

 in this section are not common but those most noticeable are calcite. 



Fig. 25. Microphotograph of nodule, from 210 Ay; slide 244; enlarged 

 4.0 diam. a, outer zone of manganese carbonate; b, core of crystalline man- 

 ganese carbonate. 



barite, and chlorite, the latter being usually associated with the 

 barite. 



219 A 10 consists of 3.5 feet of alternate layers of purple and 

 green shale which contain thin nodules and lenticles of jaspery man- 

 ganese carbonate, some of which measure 1.3 feet in length and o.i 

 feet in thickness. The lowermost subdivision of this bed, 210 A loa, 

 is a dark reddish-green heavy nodular and oolitic shale with nodules 

 very similar to those described above. Disseminated minute reddish 

 mineral particles suggesting hematite spherules are found rimming 

 the nodules in some cases. Barite occurs occasionally. Subdivision 

 b of this bed is composed of 0.2 of a foot of green and red lenticular 

 manganiferous seams with green jaspery nodules, similar to those in 

 the lower beds, interlaminated with a hematic oolitic shale. Subdi- 

 vision c, measuring 0.5 of a foot in thickness, is a dark gray oolitic and 

 slightly nodular shale with green jaspery seams. Barite blades occur 

 with nodular accumulations of manganiferous calcite. Microscopic- 

 ally this layer is essentially a hematitic oolitic shale with the indi- 

 vidual spherules measuring from 15 to 23 microns in diameter while 

 larger aggregations of spherules measure from 0.253 mm. to 0.387 

 mm. in diameter. The spherules consisting of hematite and car- 



