Maryland Geological Survey 139 



Summary of Heavy Minerals 

 Dominant. — GlaucoDite., biotite. 



Rarer. — Chlorite, epidote, muscovit.p, magnetite, tourmaline, serpentine, enstatite, 

 zircon, rutile. 



//. Clay 

 Very limonitic but also with a considerable fibrous portion. 



Summary and Conclusions. — In spite of the fact that this is a rather 

 pure sand with little clay the proportion of the finer sizes of sand, espe- 

 cially of the very fine, is remarkably large. 



The proportion of h eavy minerals is insignificant ; for if from the small 

 percentage that settled at 2.7 + is deducted the glauconite there remains 

 principally biotite, which in spite of its specific gravity is not properly 

 regarded as a heavy mineral. 



The botryoidal form of the glauconite in this sample indicates that it 

 has been formed in place. The large proportion of glauconite is unusual. 



SAMPLE NO. 6 (FIG. F, p. 169) 

 Serial number : 12. 

 Field number : 2-7-13-1911. 

 Formation : Matawan. 



Locality : Chesapeake and Delaware Canal. 



Appearance : Typical Matawan of Maryland. A dark-gray, friable, fine-grained, some- 

 what argillaceous sand, showing glauconite under the hand lens. 



Mechanical Analysis 

 Sample 9.867 gm. 



Per cent of 

 sample 



Sands 75.4 



Silt 2.2 



Clay 21.2 



Total 98.8 



Per cent of 

 total sands 



Coarse sand 1.7 



Medium sand 9.3 



Fine sand 32.6 



Very fine sand 47.7 



Extra fine sand 8.4 



Total 99.7 



Per cent of 

 very fine sand 



Light 72.3 



Heavy 26.3 



Total 98.6 



It was not at first intended to weigh the products of magnetic separation, so that a 

 large amount of the glauconitic portion was taken out for various purposes before it 

 was decided to weigh. From the weights of the. other magnetic products, however, the 

 weight of glauconite may be approximated : 



Glauconite about 95% of heavy portion = about 25% of very fine sand. 



