A Butterfly-Twin of Gypsum1

L. J. Spencer
Assistant in the Mineral Department of the British Museum.
1Communicated by permission of the Trustees of the British Museum.

Mineralogical Magazine; November 1916 v. 18; no. 83; p. 82-86; DOI: 10.1180/minmag.1916.018.83.09
© 1916, The Mineralogical Society
Mineralogical Society (www.minersoc.org)