22 BULLETIN 122, U. S. DEPARTMENT OF AGRICULTURE. 



Silt. — Minerals other than quartz, approximately 60 per cent. 

 Potash feldspars not determinable. Muscovite, 4 per cent. Feldspar 

 residues are abundant. Epidote, zircon, hornblende, chlorite, and 

 magnetite are also present. 



(19) DURHAM SANDY LOAM, SOIL. 



No. 4 sand. — Minerals other than quartz, 25 per cent. Potash 

 feldspars (orthoclase and microcline), 20 per cent. No muscovite. 

 Magnetite, biotite, and zircon are also present. 



No. 5 sand. — Minerals other than quartz, 30 per cent. Potash feld- 

 spars (microcline and orthoclase), 24 percent. Muscovite, 1 percent. 

 Unaltered feldspars. Microcline and orthoclase predominate; zircon, 

 rutile, magnetite, epidote, silhmanite, biotite, and quartz inclosing 

 both zircon and apatite are also present. The quartz grains are beau- 

 tifully clear and transparent and show no signs of chemical weather- 

 ing. 



Silt. — Minerals other than quartz, 55 per cent. Potash feldspars, 

 26 per cent. Muscovite, 2 per cent. Potash feldspars predominate; 

 biotite, zircon, and epidote are fairly abundant. Tourmaline, mag- 

 netite, and chlorite are also present. The minerals do not show signs 

 of alteration. 



(20) DURHAM SANDY LOAM, SUBSOIL. 



No. 5 sand. — Minerals other than quartz, 31 per cent. Potash 

 feldspars (microcline and orthoclase), 25 per cent. Microcline, ortho- 

 clase, and epidote predominate; biotite, muscovite, chlorite, zircon, 

 magnetite, and ilmenite are also present. There is little indication 

 of chemical weathering. 



Silt. — Minerals other than quartz, 60 per cent. Potash feldspars 

 (orthoclase and microcline), 21 per cent. Muscovite, 2.5 per cent. 

 Orthoclase, microcline, muscovite, and chlorite predominate; horn- 

 blende and rutile are also present. 



(21) YORK SILT LOAM, SOIL. 



No. 4 sand. — Minerals other than quartz, 4 per cent. No potash 

 feldspars. Muscovite, 0.5 per cent. Magnetite, tourmaline, chlorite, 

 and hornblende are also present. 



No. 5 sand. — Minerals other than quartz, 6 per cent. No potash 

 feldspars. Muscovite, 1 per cent. Chlorite, magnetite, epidote, and 

 feldspar residues are also present. 



Silt. — Minerals other than quartz, 80 per cent. No potash feld- 

 spars. Muscovite, 49 per cent. Characterized by the large amount 

 of muscovite and feldspar residues. The latter are short and long 

 needles having positive elongations and the refractive index and 



