Abstract
IN your issue of October 24, Mr. C. E. Benham calls attention to the fact that the colours of mother-o'-pearl cannot be due to the striations on the surface, as originally explained by Brewster. I have recently communicated a paper to the Geological Magazine, June 1895, in which I came to the same conclusion, and also found it impossible to accept the lamina theory as stated by Mr. Benham, for the following reasons. In certain fossilised shells, notably those of the Ammonites, the conchiolin of the shell has in course of time disappeared, and there remains not the lamina, but the prismatic structure; hence I concluded that the latter was the fundamental form in which the calcite of the shell was deposited. In Am. Ibex, Elisabethæ, &c., the shell has a chalky appearance, consisting of the detached prisms which can easily be separated by rubbing; but when the shell is carefully soaked in Canada Balsam the interspaces become filled up with the resin as they were in life, and the play of colours is perfectly reproduced. Where the original calcite has been replaced by some other mineral, such as silica or marcasite, as exemplified in the Blackdown and Gault Ammonites, it is not the lamina, but the prismatic structure that is reproduced, and in both cases the play of colours is similar to that of the original shell. In Meleagrina, whence the ordinary mother-o'-pearl is derived, the prisms of the shell are not so regular as those in the Ammonites, but the cause of the colour is the same. The laminæ of shell material, though very thin, are hardly thin enough to produce the phenomenon as Mr. Benham would have it. A full description of these prisms, and the way they affect light, is given in the paper above referred to.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
SCHWARZ, E. Colours of Mother-o'-Pearl. Nature 53, 174 (1895). https://doi.org/10.1038/053174a0
Issue Date:
DOI: https://doi.org/10.1038/053174a0
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.