OCR Text |
Show .101 manganese in solution, which latter was oxidized to peroxide with the loss of the carbonic acid. The basalt of Abiqnin forms transitions into dolerite, and contains labradorito in well- formed, comparatively large, crystals of a fine blue iridescence and partially lamellar structure. Olivine occurs in large crystals. Basalt, however, also occurs there of such dense structure that no crystalline constituents are distinguishable with the naked eye. One specimen of snch basalt, of ink- black luster, was subjected to analysis, and the following result obtained: Silicic acid 45.39 Magnetic oxide of iron 19.02 Alumina 10.51 Lime 9.97 Magnesia 9.78 Potassa 2.01 Soda 1.43 Lithia trace Protoxide of manganese trace Oxide of nickel trace Oxide of cobalt , trace Titauic acid trace Phosphoric acid trace Sulphuric acid trace 98.11 THE MOUNTAIN REGION OF ABIQUIU. Under this head is comprised the extensive mountainous region between Abiquiu, in the north, Jemez, in the south, and Nacimieuto, in the west- a regiou as nnique in topographical and geological respects as it is full of charming features and picturesque grandeur. Before considering it in detail let us take a hasty bird's- eye view of the geological structure of this section. The chief mass consists of trachyte and rhyolite, of which immense quantities have here been ejected from the interior of the earth, overflowing the Paleozoic strata which rest upon the granites. Colossal canons have been washed into the trachytes and tho underlying sandstoues. In some instances, however, the erosion has been carried down to the grauites, as in the upper portions of the Cafion Guadalupe. Strata of volcanio tufa, ofgreat thickness, have been formed- a proof that this mountain region was partly submerged for some time after the volcanic forces had ceased. But Pluto was not ouly active here during the Tertiary epochj much earlier, in the Paleozoic times, eruptive masses were thrown up. Red eruptive gneiss and granite appear in the Carboniferous strata ; the former fifteen miles north of Jemez, iu the Cafion de San Diego, the latter, six miles west of this town on a mountain. It is only the most western portious of this immense mountain region that is comparatively free from eruptive rocks. In the most northern and eastern portions we observe, along the base of the mountain mass, basaltic protrusions from Abiquiu to the month of Bear Creek; from there to Ildefonso, and tnence along the mountain base to Jemez. Near the mouth of Rio del Oso, an insignificant tributary of the Chama rising at the foot of Abiquiu Peak, tho basalt contains white crystalline zeolitic masses, partially transformed by disintegration into carbonate of lime. Carefully- selected crystals, not covered with the in-crnstating carbonate of lime, were subjected to chemical examination. The air- dry powder sustained a loss of 4.01 per cent, at 10u° C, but on ignition 16.51 per cent, more was lost. Hydrochloric acid produced a partial decomposition of the powdered crystals. A complete decomposition, however, was effected by fusion with carbonate of soda. Hydrofluoric acid also acts rapidly, and the solution obtained with it served for the determination of the alkalies. The following shows the chemical composition of this zeolite: Silica 48.21 Alumina 19.75 Lime 10.43 Soda 0.98 Potassa 1.01 Water 20.58 Total 100.96 |