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, siUimanite, 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 SDLT 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 
