The so-called ‘thermokalite’ and the existence of sodium bicarbonate as a mineral

In a brief account of the Johnston-Lavis collection of Vesuvian minerals, now preserved in University College, London, Dr. K. W. Earle mentions ‘a large number of specimens of “Thermokalite”, a new member of the Haloid group, which has, apparently, so far escaped description.’ This previously unpublished name was copied from Dr. Johnston-Lavis's manuscript labels. The late Dr. H. J. Johnston-Lavis (1856-1914) possibly considered that this mineral was the potassium compound corresponding to thermonatrite [Na2CO3.H2O]. A provisional name for an undetermined mineral having, in this way, unfortunately been published, it seemed desirable to clear up the matter. For this purpose Dr. Earle very kindly supplied two good specimens of the mineral for investigation. Access was also given to the note-books kept by Dr. Johnston-Lavis. He had made a separate entry for each specimen and the carbon copies were placed with the specimens. The entry for ‘thermokalite’ reads in every case : ‘Thermokalite (n. sp.) by Tunnel nr. Stufe di Nerone, Baja.’ This locality is situated about nine miles west of Naples in the Phlegrean Fields (Campi Phlegraei).