WATSON AND STEIGER! SPINELLITE FROM VIRGINIA 



671 



than 0.05 mm. Inclusions of magnetite and corundum, espe- 

 cially magnetite, are rather common. Thin plate-like interposi- 

 tions of magnetite or ilmenite oriented with the octahedral cleav- 

 age are observed in many spinel individuals of some sections. 

 Also the substance of the spinel is frequently crowded with minute 

 black dots in such abundance at times as almost to obscure the 

 host. These are often confined to the central portion of the 

 spinel individual like the inclusions in some leucite. Alteration 

 from weathering into a nonpleochroic isotropic reddish brown 

 substance, the composition of which has not been investigated, 

 is common in some sections. Usually the alteration product 

 forms distinct rims which strongly contrast with the unaltered 

 rich green cores of spinel. 



The composition of the spinel is shown in column I of table 2. 

 It is compared with analyses of spinel of the Peekskill emery, 

 Westchester County, New York (columns III and IV), and with 

 an analysis of spinel from the titanomagnetite spinellite of Sol- 

 nor, Norway (column V). 



TABLE 2 

 Analyses of Spinel from Virginia, New York, and Norway 



I. Spinel from Pittsylvania County, Virginia, rock emery area. George 

 Steiger, analyst. 



II. No. 1 calculated to a silica and titania free basis. 



Ill and IV. Spinel from Westchester County, New York, Peekskill rock em- 

 ery area. G. Sherburne Rogers, Ann. N. Y. Acad. Sci., 21; 69. 1911. 



V. Spinel from titanomagnetite spinellite, Solnor, Norway. J. H. L. Vogt, 

 Zeitschr. Prakt. Geol., 1900, p. 237. 



" Spinel and corundum were obtained as a residue after repeated treatment 

 with strong hydrochloric acid. Corundum was determined separately and 

 deducted. 



