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Updated: June 12, 2025
The strain to which the rock has been subjected has resulted in a very fine lamination, and it is considerably weathered. 9 Calcarous Sericite Schist. Seven Miles East of Seal Lake. A dark compact rock, in which calcite and sericite predominate. Quartz is less plentiful. The results of shearing and pressure are very prominent and bring out the foliation, even in the calcite.
"It detects differences of structure in substances not visible in ordinary light. "Light is polarized in several ways by reflection, by transmission, but most commonly through what I have here, a prism of calcite, or Iceland spar, commonly called a Nicol prism. Light fully polarized consists of vibrations transverse to the direction of the ray, all in one plane.
I thought of the countless ages it must have taken to form that monument: of the streams of clear water that had fallen and left their calcite deposits, while it grew year after year, age after age, century after century, in this profound darkness, disturbed by no noises save the rhythmic sound of the falling drops and the dull flitting of the bats, who alone were the living witnesses of its construction.
Magnetite, Titanoferrite, and Iron-pyrites also occur as normal constituents of various igneous rocks, although in very small amount, as also Apatite, or phosphate of lime. The other salts of lime, including its carbonate or calcite, although often met with, are invariably products of secondary chemical action.
In old auriferous workings which have been under water for years, in many parts of the world, formations of iron and silica have been found on the walls and roof, while in mining tunnels which have been long unused stalactites composed of silica and calcite have formed.
Planes or crystal ghosts, sometimes with pyrite crystals, marking stages of growth in the calcite crystals, are often distinguishable. The entire absence of anything like stalactites is noticeable, and together with the presence of the crystals, show that the cave was completely filled with water during their growth."
Then some little distance must be traveled along the crevice, but the angle of elevation taken by both sides of the bisected floor served as a sort of prohibitory tax together with the calcite paving, since to maintain an upright position on such a surface would require long training of a certain professional character.
In the third case are some remarkable varieties of silicates, which contain borates from Norway and other countries; and in the fourth case are the first in order, of the carbonates, including carbonates of soda, the beautiful crystals of carbonate of baryta, carbonate of strontia and aragonites, from Aragon, Hungary, Bohemia, and Vesuvius; and in the next case are deposited further varieties of aragonite, and some remarkable varieties of calcite, or carbonate of lime.
Apopholite is distinguished from calcite, as noticed under that species, and from the others by its form, difficult fusibility, and part solubility. Phrenite is characterized by its hardness, greenish color, occurrence, and action of acid. Iron pyrites is always known by its brassy metallic aspect and great hardness.
Some of the fissures may have been re-opened since they were raised beyond the reach of molten matter, and the new rent may have been filled by hydro-thermal or aqueous agencies, and may contain, along with veinstones of calcite derived from neighbouring beds of limestone, some minerals due to a previous igneous injection.
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