Calcite lenses

Sparry calcite lens interbedded with the sandstone of the Mt. Eleming Eormation (Permian) and was not associated with coal. The lenticular calcite bed was about 5 cm thick and several tens of meters wide... 

Calcium Carbonate CaC03 Calcite Aragonite Vaterite Widespread in animals and plants Exoskeleton Gravity, Ca store Eye lens... 

Figure 7.32. Geochemistry of the Devonshire, Bermuda groundwater lens. (A) Well samples and location of freshwater, (B) percentage of seawater in the groundwater, (C) saturation with respect to aragonite, (D) saturation with respect to calcite. SI (= Q) is the saturation index. (After Plummer et al., 1976.)...

It can be seen that in the region of Devonshire Marsh, located near the thickest part of the freshwater lens (Figure 7.27), that the waters are subsaturated with respect to calcite and aragonite and have high CO2 pressures, apparently derived from organic matter oxidation in the marsh area. The waters have low salinities, low Sr2+ concentrations, and little Mg2+ and Ca2+ derived from dissolution of carbonate rock minerals. Toward the south shore of Bermuda and eastward from Devonshire Marsh, the salinity of the waters increases, and the saturation state approaches near-equilibrium with calcite, and supersaturation with respect to aragonite. Lower Pc02 values characterize the waters farther away from Devonshire Marsh. 

Calcite CaCOa Algae/exoskeleton trilobites/eye lens... 

Carbonate CaCOj Calcite Aragonite Valerite Sea corals, molluscs, and many animals and plants Exoskeleton Ca-store eye lens... 

Oolitic limestones (or ooliths) are made up of tiny spherical grains (known as ooids) of 1 mm or less in diameter, precipitated by algal action in turbulent waters and cemented in calcite. Under a hand lens, they have the appearance of fish roe. 

The main consideration for the collection lens is that it should have as low an / number as feasible in order to collect as much scattered light as possible. Also, the ratio of the collection lens radius to the distance between the lens and the entrance slit should be equal to the ratio of the radius of the first optical element in the monochromator to its distance to the entrance slit. This condition will ensure that the scattered light will fill the spectrometer optics, giving optimum sensitivity and resolving power. A scrambler, such as a calcite wedge, should be placed in front of the entrance slit to scramble the polarization, since monochromators have different sensitivities to light of different polarizations. For depolarization ratio studies, a polarization analyzer is placed between the collection lens and the scrambler. 

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