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Mineralogy · Problem type
Relief from refractive index
Use this for “Garnet has n = 1.77 and the mounting medium 1.54. Is its relief low, moderate or high?”
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How strong is its relief in a medium of n = 1.54?
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A grain stands out when its n differs from 1.54: find the difference, above or below, and compare it with 0.04 and 0.12.
Assumptions
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Thin sections are glued in a medium of n = 1.54 (epoxy or Canada balsam).
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Relief is how far a grain’s refractive index is from the medium’s, in either direction.
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The 0.04 and 0.12 bounds are rough guides; the sign (above or below 1.54) is found with the Becke line.
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