234 On the Occurrence of Natro-horo-calcite in Gypsum. 



The glauber-salt was perfectly transparent on the first expo- 

 sure, and afforded a remarkably fine instance of the crystalline 

 forms of the mineral, some crystals which I saw partially efflo- 

 resced were at least 1|- inch in length. Many masses were pen- 

 etrated by perfect crystals of selenite, of various sizes, simple 

 and in macles. ^ 



The natro-boro-calcite was along with and among the crystals 

 of the preceding glanber-salt, and in some instances the latter 

 seemed to be crystallized upon the former as a nucleus, or possi- 

 bly they were in definite combinations as a totally distinct mine- 

 ral ; for crystals which at first were beautifully transparent would 

 effloresce after a day's exposure or less, and upon being placed 

 in Avater shew the silky texture peculiar to the Tiza, while plenty 

 of sulphate of soda was to be found in the water. In other 

 specimenSj the natro-boro-calcite was alone in rounded mammih 

 lated masses in the substance of the gypsum ; and these, which 

 wxre of all sizes up to that of a pigeon's egg or so, on being 

 broken, presented the appearance of a finely fibrous silky -lustrous 

 mass brilliantly white in color. 



The purest pieces had a specific gravity of 1'65; hardness 



1; were tough between the teeth; tasteless; scarcely solubler 

 in water ; before the blowpipe, melted with ease to a transparent 

 bead. 



On comparing the circumstances of this occurrence with those 

 referred to in the remarks of Professor Anderson, before quoted, 

 and some other facts I think they are very interesting. In the 

 gypsum of Nova Scotia we have a new and distinct locality for 

 the rare mineral natro-boro-calcite which is analogous with that 

 of a species chemically allied,* boracite (MgO BO 3), found in the 

 gypsum of Holstein, and a compact boracite forming beds with 

 rock-salt and gypsum at Stassfurth in northern Germany. 



With these exceptions, boracic acid is found, as is well known, 

 either in directly volcanic regions, most abundantly as such or 

 as borax, and a well marked case of actual sublimation of the 

 acid, from a volcano in the Island of Vulcano near Sicily has 

 been studied by Warrington ;t or in smaller amount in minerals 

 the products of recent or extinct volcanoes, as IIumboldtite,:f 

 from ejected blocks of Vesuvius and zeolites, and Datholite from 

 trap of Salisbury Craigs, New Jersey, and other places; or in 

 minerals of purely plutonic or metamorphic rocks, as tourmaline 

 the rhodizite of Rose, and axinite; the species which contain it 

 at all being few in number. It may be noticed also that traces 

 of this acid have lately been met with in the Kochbrunnen of 

 Wiesbaden J and in the waters of Aachen. 



* Nijol's Mineralogy, p. 305. f WeHs* Annual, 1856, p. S.-^S. 



i :Nicor3 mueralogy, p. 307. g Liebig und Kopp's JabresWicht, 1862, p. 31.^^. 



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