14 PROCEEDINGS OF THE NATIONAL MUSEUM vol.72 



based largely upon the artificially prepared material, although they 

 describe one natural example. The materials of their experiments 

 were obtained by shaking precipitated magnetite with oxidizing 

 agents at ordinary temperatures. They found that heating destroys 

 the magnetic character of ferromagnetic ferric oxide and that hema- 

 tite can not be converted into the magnetic modification of the com- 

 pound. It was also found that dehydration of goethite and limonite 

 would yield only nonmagnetic Fe203, although lepidocrocite, when 

 dehydrated, did yield the magnetic FeoOg. 



The example of natural magnetic ferric oxide described by Sosman 

 and Posnjak was also polarized. It was in the form of a light choc- 

 olate-brown powder containing yellowish brown specks and came 

 from a gossan deposit at Iron Mountain in the Shasta County copper 

 district, Calif., where it was collected by Drs. L. C. Graton and 

 B, S. Butler. This material upon analysis gave the following: 



Insoluble 1. 80 



Fe.03 , 85. 30 



FeO 2. 40 



OaO . Trace. 



H2O to red heat 3. 10 



Other volatile matter 2.50 



95.10 



No discussion of the probable origin of this material is given by 

 these authors beyond the statement that it is in a gossan and contains 

 some pyrite. They suggest the advisability of giving the material a 

 new mineral name but consider it desirable, before so doing, to have 

 a type specimen less contaminated with impurities. 



MARTITE FROM CERIIO MERCADO, DURANGO 



In connection with his studies of the iron ores of the Cerro Mer- 

 cado, near the city of Durango, Durango, Mexico, Dr. W. F. Foshag 

 found material, evidently martite since it showed the crystal form of 

 magnetite yet revealed little magnetite on polished surface. This 

 had a magnetic susceptibility in excess of that which could be ex- 

 plained by the visible magnetite inclusions. For comparison with 

 the ferromagnetic ocher from Oklahoma and the oxidized meteoric 

 irons, a sample was briefly examined. 



The specimen, from " Penascos de la Industria " is a heavy cellu- 

 lar mass of reddish black color and metallic luster. The cavities 

 are lined with lustrous and brilliant octahedral crystals which are 

 thinly coated with small amounts of various later minerals. When 

 ground to pass 80 mesh the color of the powder is chocolate {7'^-ny) 

 Kidgway. Upon being worked over with a hand magnet 78 per cent 

 was separated as attracted while the remaining 22 per cent was 



