For 11 crystals of the amblygonite-montebrasite series LiAlPO₄(F,OH) ranging in composition from 4.0 to 91.8 mole percent fluorine with only two containing significant sodium, 2V and principal refractive indices were determined to 0.5° and 0.0005, respectively, by spindle-stage methods. If F < 60 mole percent, as is true for the vast majority of natural specimens, fluorine can usually be estimated to within 2 mole percent from the equation
F = -66.3 + 1.08 * 2V<sub>Z</sub>
as well as from similar regression equations involving the refractive indices α, β, and γ. Above 60 mole percent F, the optical properties are less sensitively (and non-linearly) related to fluorine content. Estimates of F proved feasible despite significant substitution of Na for Li. By contrast, this substitution may introduce significant errors when estimating F by methods involving lattice parameters.
Progressive substitution of (OH), a natural dipole involving a covalent bond, for the relatively non-polarizable F anion caused all three principal refractive indices to increase; γ increases more than α or ß because its corresponding principal vibration direction Z becomes sub-parallel to the O···H vector in the structure as (OH) content increases. / Master of Science / incomplete_metadata
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/50060 |
| Date | January 1986 |
| Creators | Greiner, Daniel Joseph |
| Contributors | Geological Sciences |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis, Text |
| Format | vii, 46 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 15179073 |
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