ON SIDERITE AND ASSOCIATED MINERALS FROM THE 
COLUMBIA RIVER BASALT AT SPOKANE, 
WASHINGTON. 
By Earz V. SHANNON, 
Assistant Curator, Department of Geology, United States National Museum. 
INTRODUCTION. 
Some years ago Mr. Henry Fair, of Spokane, Washington, noted 
that the rock of the Columbia River lava flows being excavated in 
the city of Spokane contained vesicular cavities in which were de- 
veloped unusual minerals, most abundant and conspicuous among 
which was siderite in the peculiar spherical forms commonly called 
sphaerosiderite. Mr. Fair carefully selected a large collection of the 
best of the specimens of this material for preservation in the Eastern 
Washington State Museum and a number of duplicates was sent to 
the New York Mineralogical Club for distribution among the members. 
One specimen from this lot was sent to the National Museum by 
L. P. Gratacap. An analysis of the siderite having been made by 
J. P. Maider, city chemist of Spokane, the optical properties were 
measured by Larsen and the data published by Wherry and Larsen.! 
These results have since been again used by Gaubert.? 
Mr. Fair has desired that the material be given a more general and 
detailed study and that, if of sufficiently general interest, the results 
be published. To this end he recently donated a representative 
series of specimens from the locality to the National Museum. These 
have been studied in the Museum laboratory, with results as below. 
The minerals identified include feldspar (oligoclase-andesine), 
magnetite, cristobalite, siderite, pyrite, iron opal, hyalite, calcite, 
aragonite, barite, limonite, and goethite. One of the most interesting 
though least conspicuous of these is the cristobalite, which occurs in 
well-formed crystals which it has been possible to measure on the 
goniometer. ‘The paragenesis and association of the minerals of the 
1 Edgar T. Wherry and Esper S. Larsen. The indices of refraction of analyzed rhodochrosite and 
siderite. Journ. Wash. Acad. Sci., vol. 7, pp. 365-368, 1917. 
2P.Gaubert. The indices ofrefraction of the rhombohedral carbonates. Bull. Soc. Franc. Min., 
vol. 42, pp. 88-120, 1919. 
No. 2458.—PROCEEDINGS U. S. NATIONAL MUSEUM, VOL. 62, ART. 12. 
60466—23—Proc.N.M.vol.62 32 1 
