Although the Mendip Hills, as a district, have from time to time received the attention of geologists, details of the mineral occurrences are, on the whole, remarkably scarce. Mining was formerly carried on on the Hills for many centuries, but mineralogy as a science had not been sufficiently developed at the time when the mines were most active, and little interest was taken in the minerals other than those suitable or required for commercial and industrial purposes. Even in later years, when, in the course of treating old refuse and tailings left by earlier miners and of various attempts to resuscitate the mining industry, much material must have been available for examination, little attention seems to have been paid to it, or to the numerous quarries that were opened in the Carboniferous Limestone.

In a previous paper describing the geological and petrographical details of the adinoles of Dinas Head, short references were made to the common occurrence among the adinoles and associated rock-types of the magnesia-rich tourmaline, dravite. It is proposed now to describe these tourmaline-rich rocks in more detail and to discuss the question of their origin.

Adinoles with accessory tourmaline occur wherever true adinoles are developed at Dinas Head, although tourmaline is characteristically absent from types 2 a, b, c, and 3 [1, pp. 318–323]. Bands with up to 30 % tourmaline occur interbanded with normal adinoles of type 1 and with certain spilosites.

In the mineralogical literature, stibnite is usually stated to change by oxidation into kermesite and finally into valentinite or senarmontire. Another alteration product is described as antimony ochre, a term loosely applied to several minerals, viz. cervantite, stibiconite, and volgerite (Dana, System of mineralogy, 6th edit., 1892, p. 203).

In my metallurgical experience with stibnite ores, I have never met with kermesite or valentinite. Whenever I have encountered altered stibnite in ores from widely separated localities, it showed a yellowish to buff coating which I took to be cervantite. After spending two years in central China where I examined hundreds of tons of stibnite ores from Hunan province, I had to purchase a specimen of kermesite from a mineral dealer in order to become acquainted with the mineral. The locality of the specimen was given as Bräunsdorf, Saxony.

Large specimens of native gold showing crystalline form are not at all common in Southern Rhodesia, but the recently discovered gold with adherent silver from the Old West mine, Penhalonga, would be outstanding wherever it had been found.

About the middle of December 1940, Mr. D. V. Burnett, Director and Consulting Engineer to the Rezende Mines Limited, the owners of the property, lent two specimens to the Geological Survey for examination. The following week Mr. B. Lightfoot, Director of the Southern Rhodesia Geological Survey, visited the mine and examined the cavity where the specimens had been found. He made notes and collected specimens of the associated minerals, and borrowed a few other specimens which had been retained at the mine.