in the cut perpendicular to the optic axis 2V, it
is determined according to the curve of the isogyre, as shown in the diagram
(see figure 1).Determination
of the angle formed by the two optic axes (2V)
This can be determined in two cuts.
in the cut perpendicular to the optic axis 2V, it
is determined according to the curve of the isogyre, as shown in the diagram
(see figure 1).
in the cut perpendicular to the acute bisectrix,
it is calculated according to the distance between the bands of the isogyres,
as shown in the diagram (the distance separating the two melatopes; figure 2).
This is not actually exactly 2V (it is an approximate value) and is known as the apparent optic angle (2E) (figure 3). To calculate the true value of 2V, the refractive indices of the mineral must be considered in order to correct the calculated value 2E in the interference figure..
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