428 Reviews— United States Geological Survey. 
Reservation. Placer mining started at La Paz as early as 1862, 
but was almost entirely abandoned a few years later. The placer 
areas in Dome Rock Mountains and Plomosa Mountains are composed 
of intrusive igneous rocks, some of schistose character and others 
of holocrystalline granitic texture. The schist is believed to be of 
pre-Cambrian, and the granite probably of Mesozoic age. The belt 
of cinnabar deposits described by Mr. Adolph Knopf is situated in 
the heart of the Pilot Mountains, about 8 miles south-east of Mina, 
Esmeralda County. They came to light in June, 1913, but there 
were signs of much earlier exploration. The main area comprises 
the hill now known as Cinnabar Mountain, which is composed of. 
limestones interstratified with dolomitic greywacke. The limestones 
carry crinoid fragments and other obscure fossils, and are probably of 
Paleozoic age; the cinnabar is intergrown with calcite and dolomite. 
Northwards greywacke, slate, and chert form the country rock ; here 
the mineral occurs in a gangue of barytes. Other deposits are 
situated 6 miles east of Beatty, Nye County, in the Fluorine mining 
district, partly on Bare Mountain and partly on Yueca Mountain. 
The general country rock is a fine-grained grey dolomite, of Silurian 
age, which is massively bedded and much distorted. Cinnabar is 
associated with opal and alunite. The genetic relation of the 
cinnabar deposits to the many gold deposits scattered throughout 
the Western Nevada quicksilver belt constitutes an interesting 
problem for future research. 
Mr. Ernest F. Bouchard describes the iron-ores in Cass, Marion, 
Morris, and Cherokee Counties, Texas, and also the iron-bearing 
deposits in Bossier, Caddo, and Webster Parishes, Louisiana. In the 
first instance the surface rock formations consist chiefly of sand, clay, 
gravel, and silt. The most recent deposits are of Quaternary age, 
but the main masses which contain the iron-ore deposits are of 
early Ternary age (Eocene). he limonite deposits in Louisiana 
occur mostly in unconsolidated sandy clay and sand, which may 
be assigned to the St. Maurice formation of the Claiborne group 
(Eocene). 
A reconnaissance of the Cottonwood—American Fork mining 
region, Utah, made by Mr. B.S. Butler and Mr. G. F. Loughlin, 
is a description of the ore deposits which will be included in a 
general report on the entire State, but has been issued separately 
in advance on account of the exceptional interest now being shown in 
the region. The silver-lead mines, which were discovered in 1864 
and have been worked intermittently ever since, have proved very 
productive, but the heavy working expenses have previously militated 
against their success. The sedimentary rocks may be divided into 
two main groups—the quartzite and shale series, of pre-Cambrian and 
Cambrian age, and the great limestone series, which is mostly of 
Mississippian (Lower Carboniferous) age. The two main intrusive 
bodies of igneous rocks are the Little Cottonwood stock of granodiorite 
on the west, and the Clayton Peak stock of quartz diorite on the east 
of the region. The structure of the district is complex, and is 
characterized by considerable faulting. As a general rule the 
greatest mineralization occurs towards the top of the intrusive stocks 
