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Note on the Refrative Indices of Pyromorphite, Mimetite, and Vanadinite

Published online by Cambridge University Press:  14 March 2018

H. L. Bowman
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Extract

It is somewhat remarkable that a group of minerals, of which such excellent transparent crystals are known as of pyromorphite, mimetite, and vanadinite, should not have hitherto been submitted to a detailed optical examination, except as regards the nature of the interference figures visible in a cross-section. The only reference to the refractive indices of these substances, which I have been able to find, is one by Schroeder van der Kolk, who states that those of pyromorphite amt vanadinite are above 1.93 (as found by immersion in highly refracting liquids), and that they have a birefringence of 0.02 and 0.01 respectively.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 13 , Issue 62 , December 1903 , pp. 324 - 329
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1903

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References

Page 324 note 1 ‘Natural History of Precious Stones and Metals,’ 1883, p. 288.

Page 324 note 2 ‘Delle Pierre Antiche,’ Roma, 1828, p. 170.

Page 324 note 3 Centralblatt f. Mineralogie, 1900, p. 291.

Page 324 note 4 Zeits. anal. Chem, 1899, Jahrg. xxxviii, p. 656.

Page 325 note 1 If the true value of ∊ be calculated from the observed indices and θ, the result obtained in the worst case (No. 4) does not differ from the observed value by so much as one in the fourth place of decimals.

Page 325 note 2 Nature, 1885, vol. xxxi, p. 263.

Page 326 note 1 Each of the two faces gave two equally good images of the goniometer-signal 4′ apart. The prism-angles corresponding to these images are 32° 13′, 32° 17′, 32° 21′. The effective refracting angle is here taken as the mean (= 32° 17′). The difference in the refractive index caused by taking one of the extreme values would be about 0.0024.

Page 326 note 2 The lettering of the forms is that used by Dana (System, 1892), vlz. :—a {112̄0}, m {101̄0}, c {0001}, y {202̄1}, x {101̄1}, u {213̄1}, s {112̄1}.

Page 326 note 3 θ = inclination of the optic axis to the plane bisecting the prism-angle.

Page 329 note 1 Chem. News, 1882, vol. xlvi, p. 215.