IKON ORES. 237 



SPECULAR IRON ORE. — HEMATITE. 



Rhombohedral. In complex modifications of a rhombchc 



dron of 85° 58' ; crystals occasionally thin tabular. Cleavage 

 usually indistinct. Often massive granular ; sometimes 

 lamellar or micaceous. Also pulverulent and earthy. 



Color dark steel-gray or iron-black, and often when crys- 

 tallized having a highly splendent luster ; streak-powder 

 cherry-red or reddish-brown. The metallic varieties pass 

 into an earthy ore of a red color, having none of the external 

 characters of the crystals, but perfectly corresponding to them 

 when they are pulverized, the powder they yield being of a 

 deep red color, and earthy or without luster. Gr=4.5 — 

 5 # 3. Hardness of crystals 5*5 — 6*5. Sometimes slightly 

 attracted by the magnet. 



Varieties and Composition. 



Specular iron. Specimens having a perfectly metallic 

 luster. 



Micaceous iron. Specular iron, with a foliated structure. 



Red hematite. Submetallic, or unmetallic, and of a brown- 

 ish-red color. 



Red ocher. Soft and earthy, and often containing clay. 



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

 of a fine texture. 



Jaspery clay iron. A hard impure ore, containing clay, 

 and having a brownish-red jaspery look and compactness. 



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

 pearance less like jasper. 



This is one variety of what is called "clay iron stone." 

 Much of it belongs to the following species, and a large 

 part also is spathic iron, as is the case with that of the Eng- 

 lish coal measures. 



Lenticular argillaceous ore. A red ore, consisting of 

 small flattened grains, something like an oolite. 



Oligiste iron, iron glance, and rhombohedral iron ore, are 

 other names of the species specular iron. 



What is the crystallization of specular iron 1 What are its physical 

 characters 1 Describe the varieties. 



