444 REPORT OF NATIONAL MUSEUM, 1899. 



Canada (Specimen No. 59927, U.S.N.M.) and Spain (Specimen No. 

 40011, U.S.N.M.). 



According to G. H. Stone, 1 the asphaltic sandrock of western Colo- 

 rado and eastern Utah consists of grains of sand which are in contact 

 with one another, the spaces between the grains being filled with 

 asphalt, the proportioned amount of which varies up to 15 per cent by 

 weight, or 27 per cent by volume. The thickest stratum of fully 

 charged rock in the region described was nearly 40 feet in thickness, 

 though usually the strata of high-grade material are not more than 4 

 to 10 feet thick and alternate with others which are quite poor or 

 barren, so that the amount of "pay rock" is often grossly exaggerated. 



Shales and marls may often be so highly charged with bituminous 

 matter as to be nearly or quite black, and even approach cannel coal in 

 composition, though much richer in ash. Those of Colorado and Utah, 

 according to Stone, contain but from 10 to 20 per cent of carbona- 

 ceous matter, though burning readily with a bright flame. They are 

 of Tertiary age. Asphaltic sands and sandrocks are of common occur- 

 rence in Kern, San Luis Obispo, Santa Barbara, Santa Cruz, Ventura, 

 and other counties in California, and in some cases are quite exten- 

 sively utilized. 2 



In Ventura County the material is reported as occurring in the form 

 of a fissure vein in siliceous clay, of Miocene age, the vein being from 

 7 to 15 inches thick on the surface, but widening rapidly in descent to 

 a thickness of 5 feet at a depth of 65 feet (Specimens Nos. 67675, 67676, 

 U.S.N.M.). This material is as taken from the vein far from pure 

 asphalt, but rather an asphaltic sand. The Las Conchas Mine in Santa 

 Barbara County consists of a body of sand soaked with maltha, embrac- 

 ing an area of 75 acres and estimated to be 25 feet or more in thickness. 

 At the Pacific Asphalt Company's mine the asphalt occurs in irregular 

 masses and veinlike bunches in soft, sandy clay, and is said to be 50 to 

 60 per cent pure. 



On the Sisquoc Grant, 8 miles north of Los Alamos are two very 

 large deposits, one some 10,560 feet long, 500 feet wide, and averag- 

 ing 300 feet in thickness, and the other 5,000 feet long, 800 feet wide, 

 and 100 feet thick. In Santa Cruz County there are enormous deposits 

 of bituminous rock lying in nearty horizontal strata in the foothills 

 facing the coast west and north of the city of Santa Cruz. The beds 

 have been extensively eroded so that the outcrops occur in irregular, 

 detached hillocks. At one of the open cut mines the materials lie as 

 follows: 



Feet. 



Light-colored shales 60 



Massive bituminous rock 30 



Very soft sandstone 8 



Massive bituminous rock. . . 12 



1 American Journal of Science, XLII, 1891, p. 148. 



2 See Thirteenth Annual Report State Mineralogist of California, 1894. 



