 | Geological and Geographical Survey of the Territories (U.S.) - 1872 - 524 sider
...manufactured into fire-bricks of excellent quality. Clay iron-stone is occasionally interstratified with the clays and black shales, and in Boulder County,...subsequently by atmospheric agency into those brown hydrates. The coal-beds are often of great size, the largest now worked being twenty-six or twenty-seven... | |
 | Geological and Geographical Survey of the Territories (U.S.) - 1872 - 542 sider
...manufactured into fire-bricks of excellent quality. Clay iron-stone is occasionally interstratified with the clays and black shales, and in Boulder County,...the lighter materials of the strata containing them wore removed, and converted subsequently by atmospheric agency into those brown hydrates. The coal-beds... | |
 | Geological and Geographical Survey of the Territories (U.S.) - 1872 - 526 sider
...manufactured into fire-bricks of excellent quality. Clay iron-stone is occasionally interstratified with the clays and black shales, and in Boulder County, Colorado, the summits rtnd sides of some of the hills near the coal-mines are partially covered with masses of brown iron... | |
 | JAMES MACFARLANE. A.M. - 1873 - 718 sider
...manufactured into fire-bricks of excellent quality. Clay iron-stone is occasionally interstratified with the clays and black shales; and in Boulder County,...coal-mines are partially covered with masses of brown iron-ore, that have the appearance of solid ledges; but which were no 1 By Dr. Hayden's report of 1871,... | |
 | James Macfarlane - 1873 - 740 sider
...of 1871, they appear to be Cretaceous, or a transition series between the Cretaceous and Tertiary. doubt collections of clay iron-stone, left behind...subsequently by atmospheric agency, into those brown hydrates." The CoalrSeams. " The coal-beds are often of great size, the largest now worked being 26... | |
 | Geological Survey of Canada - 1873 - 646 sider
...perhaps the predominant material of the formation. It occurs in beds of great thickness, especially in Colorado, the summits and sides of some of the hills near the coal mines are partially covered with masses of brown iron-ore that have the appearance of solid ledges,... | |
 | Jacob Harris Patton - 1891 - 152 sider
...The Masses of Iron-Ore. — Iron exists in detached beds in the east region of the Rocky Mountains. In Boulder County, Colorado, the summits and sides of some of the hills near where the coal-mines are found are partially covered with masses of brown iron-ore. We possess perhaps... | |
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Newberry, are probably an undescribed species. Fire-clay is perhaps the predominant material of the formation. It occurs in beds of great thickness, especially in Colorado, and at Golden City it is manufactured into fire-bricks of excellent quality. Clay... 