112 HOW CROPS FEED. 
We might give in the same style formule for all the 
minerals noticed in these pages, but for our purposes this 
is unnecessary. 
Amphibole is an abundant mineral often met with in 
distinct crystals or crystalline and fibrous masses, varying 
in color from pure white or gray (tremolite, asbestus), light 
green (actinolite), grayish or brownish green (anthophyl- 
lite), to dark green and black (hornblende), according as 
it contains more or less oxides of iron and manganese. 
It is a silicate of magnesia and lime, or of magnesia and 
protoxide of iron, with more or less alkalies. 
White. Gray. Ash-gray. Black. Leek green, 
Gouverneur, Lanark, Cummington, Brevig, Waldheim, 
N. Y. Canada. Mass. Norway. Saxony. 
Rammelsberg. T.S. Hunt. Smith & Brush. Plantamour. Knop, 
Silica, 57.40 55.30 50.74 46.57 58.71 
Magnesia, 24.69 22.50 10.31 5.88 10.01 
Lime, 13.89 13.36 trace 5.91 11.53 
Protoxide of 
iron, 1.36 6.30 33.14 24.38 5.65 
Protoxide of <= trace 1.97 2.07 aie 
manganese, 
Alumina, 1.38 0.40 0.89 3.41 1.52 
Soda, — 0.80 0.54 7.9 12.38 
Potash, — 0.25 trace 2.96 — 
Water, 0.40 0.30 3.04 — 0.50 
Pyroxene is of very common occurrence, and consider- 
ably resembles hornblende in colors and in composition. 
White. Gray- White. Green. Black. Black. 
Ottawa, Bathurst, Lake Orange Co., Wetterau, 
Canada. Canada. Champlain. je 
T.S. Hunt. T.S. Hunt. Seybert. Smith & Brush. Gmelin. 
Silica, 54.50 51.50 50.38 39.30 ~ 56.80 
Magnesia, 18.14 17.69 6.83 2.98 5.05 
Lime, 25.87 23.80 19.33 10.39 4.85 
Protoxide 1.98 — 20.40 30.40 12.06 
ofiron, 
Sesquioxide ss 0.35 
of iron, 
Protozideof = trace 0.67 8.72 
manganese, 
Alumina, _ 6.15 1.83 9.78 15.32 
Soda, — — — 1.66 3.14 
Potash, — — — 2.48 0.34 
Water, 0.40 1.10 — 1.95 —_— 
