IRON. 177 



Red chalk. More firm and compact than red ochre, and 

 of a fine texture. 



Jasper y clay iron. A hard impure siliceous clayey ore, 

 and having a orownish-red jaspery look and compactness. 



Clay iron stone. The same as the last, the color and ap- 

 pearance less like jasper. But this is one variety only of 

 what is called "clay iron stone," a name covering also a re- 

 lated variety of siderite and limonite. 



Lenticular argillaceous ore. A red ore, consisting of 

 small flattened grains. 



Martite is hematite in octahedrons, derived, it is supposed, 

 from the oxidation of magnetite. 



Composition. Fe0 3 =Oxygen 30, iron 70=100. B.B. 

 alone infusible. Heated in the inner flame it becomes 

 strongly magnetic. 



Dijf. The red powder of this mineral, and the magnetism 

 which is so easily induced in it by a redaction flame dis- 

 tinguish hematite from all other ores. The word hematite, 

 from the Greek haima, blood, alludes to the color of the 

 powder. 



Obs. This ore occurs in crystalline and stratified rocks of 

 all ages. The more extensive beds of pure ore abound in 

 Archaean rocks ; while the argillaceous varieties occur in 

 stratified rocks, being often abundant in coal regions and 

 among other strata. Crystallized specimens are found also 

 in some lavas, as a volcanic product. 



Splendid crystallizations of this ore come from Elba, whose 

 beds were known to the Romans ; also from St. Gothard ; 

 Arendal, Norway ; Longbanshyttan, Sweden ; Lorraine and 

 Dauphiny. Etna and Vesuvius afford handsome specimens. 



In the United States, this is an abundant ore. The two 

 Iron Mountains of Missouri, situated 90 miles south of St. 

 Louis, consist mainly of this ore, piled " in masses of all 

 sizes from a pigeon's egg to a middle-si e church." One of 

 them is 300 feet high, and the other, the " Pilot Knob," is 

 700 feet. The massive and micaceous varieties occur there 

 together with red ochreous ore. Large heds occur in Essex, 

 Sfc. Lawrence and Jefferson counties, N. Y., and at Mar- 

 quette, in Michigan; the micaceous variety, atHawley, Mass., 

 Pierrnont, N. H., and in Stafford County, Va. ; lenticular 

 argillaceous ore abundantly in Oneida, Herkimer, Madison 

 and Wayne counties, "N. Y. , constituting one or two beds of 

 the Clinton group (Upper Silurian), in a compact sandstone ; 



