1874.] Mineralogy. 409 
planes, and in some cases twinned so as to exhibit the characteristic re-entering 
angles. 
MINERALOGY. 
A mineralogical paper of considerable interest has been communicated to 
the American Academy of Arts and sciences by Prof. J. P. Cooke, jun., in 
which he reviews the history of those micaceous minerals which may be 
grouped together under the general name of Vermiculite. This name was 
originally applied by Mr. T. H. Webb to a peculiar mineral which at the time 
of its discovery excited much interest by its curious behaviour when heated ; 
the substance exfoliated prodigiously, and the little scales opened out in worm- 
like threads, which suggested the original name. This remarkable exfoliation 
and the apparent increase in volume are referred by Prof. Cooke to the loss 
of water of crystallisation, and may be compared with the well-known 
efflorescent phenomena presented by the dehydration of certain crystalline 
salts. Other minerals possessing similar pyrognostic characters have since 
been discovered, and a comparison of these minerals has led the author to 
extend the use of Vermiculite as a family name. Three distin species are 
now included in this group: first, ¥efferisite, a mineral discovered by Mr. W. 
Jefferis at West Chester, Pa., and described by Prof. Brush; secondly, 
Hallite, a new species founded by Prof. Cooke on specimens collected by Mr. 
J. Hall at East Nottingham, Chester Co., Pa.; and thirdly, Culsageeite, 
another new species discovered in Col. Jenks’s Culsagee Mine in North 
Carolina, which mine has yielded the remarkable specimens of corundum 
noticed in our report last quarter. Prof. Cooke discusses in much detail the 
crystallographic, optical, and chemical characters of Jefferisite, Hallite, and 
Culsageeite, with special reference to their relation to the group of micas. 
Our knowledge of the mineralogy of the Argentine Republic is much in- 
creased by a paper recently communicated to Tschermak’s ‘* Mineralogische 
Mittheilungen”’ by Dr. A. Stelzner, who was appointed a few years ago 
Professor of Mineralogy in the University of Cordoba. The Sierra of Cordoba, 
rising like an island from the surrounding pampas, is composed of three 
parallel ridges, which consist principally of crystalline slates associated with 
masses of granite in which are large quartz-stocks containing minerals of 
considerable interest. Although consisting chiefly of quartz, these stocks 
invariably contain mica, as well as large crystals of orthoclase-felspar. 
Beryl is also found in six-sided prisms of unusual size, whilst apatite and 
triplite occur subordinately. But the most interesting of this group is the 
rare mineral columbite, specimens of which have been analysed in Cordoba 
by Dr. Siewert. Another series of minerals described by Stelzner occurs in 
crystalline limestones, associated with the metamorphic rocks of the Sierra. 
Prof. A. H. Church has communicated to the ‘‘ Chemical News” his 
analysis of Ashantee gold. Those who are familar with the fine collection of 
nuggets and ornamental objects lately exhibited by Messrs. Garrard will 
remember that most of the specimens presented a rich colour, heightened by 
association with a red ferruginous earth, more or less adherent to the surface. 
Church’s analysis gave—Gold, go°055 ; silver, 9'°940; iron and copper, traces. 
The same chemist has also published in the ‘‘ Chemical News ”’ his analysis 
of some clean grain-gold from a burn at Wanlock-head in Dumfriesshire. A 
good deal of historical interest clings to the gold-fields of Southern Scotland, 
though well-nigh forgotten at the present day. Worked by Sir Bevis Bulmer 
in the sixteenth century, they yielded the gold from which the unicorns and 
the bonnet-pieces of James IV. and V. were coined. It was these mines, 
too, that were at one time to be worked by a company of twenty-four gentle- 
men to be created “* Knights of the Gold Mines.” At present, however, the 
Clydesdale washings yield only specimens for the cabinets of the curious. 
Prof. Church finds the Wanlock-head gold to contain—Gold, 86:60; silver, 
12°39; iron, 0°35. A specimen of Sutherlandshire gold has yielded to Mr. G. 
H. Makins 79°22 per cent of gold and 20°78 per cent of silver. Pliny tells 
us that when the proportion of silver in gold exceds one-fifth, the substance is 
