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Updated: June 17, 2025
In many cases, however, the early history of a metamorphic rock can be deciphered. Fossils not wholly obliterated may prove it originally water-laid. Schists may contain rolled-out pebbles, showing their derivation from a conglomerate. Dikes of igneous rocks may be followed into a region where they have been foliated by pressure.
The geologists were interested, and we others learnt something of olivines, green in crystal form or oxidized to bright red, granites or granulites or quartzites, hornblende and feldspars, ferrous and ferric oxides of lava acid, basic, plutonic, igneous, eruptive schists, basalts &c. All such things I must get clearer in my mind. Tuesday afternoon a cold S.E. wind commenced and blew all night.
The whole of this part of the country is composed of marly tufa, containing the same kind of shells as those at present alive in the seas. As we advanced eastward and ascended the higher lands, we found eruptive trap, which had tilted up immense masses of mica and sandstone schists.
Between it and the contorted schists we passed over some soft, decomposing trap-rocks, which, both here and elsewhere, appeared to intervene between these two formations. Over the whole country between Ocotal and Totagalpa were spread many large boulders, great blocks of conglomerate, and of a hard blue trap-rock that I did not see in situ, lying on the upturned edges of the schistose rocks.
Even at three thousand feet he gave me a chill.... But let Whinney speak. "It is plain," he said, "that the basalt monadnock on which we stand is a carboniferous upthrust of metamorphosed schists, shales and conglomerate, probably Mesozoic or at least early Silurian." At this point our wives burst into laughter. In fact, their attitude throughout was trying but Whinney bravely proceeded.
This cement is composed of angular quartz-fragments, broken from the reefs or veins, and fragments of diorite and hornblende schists, cemented together by lime; it is very hard and solid and, in places, continues to a depth of over twenty feet. The gold is extracted from these depths by crushing and dry-blowing.
The name Pamozima means, "the departed spirits or gods" a fit name for a place over which, according to the popular belief, the disembodied souls continually hover. The rock lowest down in the series is dark reddish-grey syenite. This seems to have been an upheaving agent, for the mica schists above it are much disturbed.
GEOLOGICAL SECTION NEAR OCOTAL. Section of Strata between Depilto and the hill three miles south-west of Ocotal. Gravel with boulders of trap and conglomerate. Gravel with boulders of gneiss and quartz rock. Contorted schists. The evidences of glacial action between Depilto and Ocotal were, with one exception, as clear as in any Welsh or Highland valley.
They were probably mud and sand and limestone when first made, but they have been changed to mica schists, gneiss, granite, marble, and other crystalline rocks. When any rock becomes crystalline, the fossils dissolve and disappear, as coins lose their stamp and form when they are melted in the jeweller's gold-pot.
BRITISH. Bituminous schists of Gamrie, Caithness, etc., with numerous fish. BRITISH. Arbroath paving-stones, with Cephalaspis and Pterygotus. FOREIGN. Oriskany sandstone of Western Canada and New York. BRITISH. Upper Ludlow formation, Downton sandstone, with bone-bed. FOREIGN. Niagara limestone, with Calymene, Homalonotus, etc. BRITISH. Bala and Caradoc beds.
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