Article Published: 13 February 1954 Visual Purple Level and the Course of Dark Adaptation W. A. H. RUSHTON & R. D. COHEN Nature 173, 301–302 (1954) Cite this article ...
This 17.53-carat amethyst displays a rich reddish purple color. - Lydia Dyer, Super Trillion Cut Amethyst gem courtesy of John Dyer & Co. Amethyst has been the most-prized quartz variety for centuries ...
Some results have been hidden because they may be inaccessible to you
Show inaccessible results