1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 105 



ON THE SERPENTINE OF MONTVILLE, NEW JERSEY. 



BY GEORGE P. MERRILL. 



(With Plates xxxi, xxxn. ) 



Being in common with petrographers in general deeply interested in 

 the problem of the origin of serpentinous rocks, the writer took occa- 

 sion, during the summer of 1SS7, to visit sundry localities where the 

 rock was known to occur, and among them, that at Moutville, N. J. 

 This locality was looked forward to with especial iuterest, since owing 

 to the rare beauty, purity, and compactness of the rock, as shown in 

 numerous mineral cabiuets throughout the country, and its known oc- 

 currence imbedded in a massive dolomite, it was thought that here, if 

 anywhere, it might be found as a rock formed from aqueous sediments 

 of chemical origin, as argued by Dr. Hunt.* The results of my exami- 

 nations are given below: 



As above noted, the serpentine occurs associated with a massive, 

 coarsely crystalline dolomite, and the fine specimens to be found in the 

 various museums are obtained during the process of quarrying this rock 

 for burning into quicklime or for a flux in iron furnaces. 



The first noticeable thing regarding the serpentine is, that while it 

 is occasionally found in small seams and veins, its principal mode of 

 occurrence is the form of isolated nodules from a few inches to 1 or 2 

 feet in diameter, or as a thin coating on large irregularly rounded or 

 oval bowlder like masses of all sizes up to 8 or 10 feet iu diameter, 

 and which from their crystalline texture and white or gray color seem 

 in most instances to have been mistaken for the ordinary dolomite of 

 the quarry. 



The smaller nodules separate readily from the inclosing dolomite, and 

 present always highly polished and often beautifully grooved and sliek- 

 eu sided surfaces, which are covered here and there with patches of a 

 thin foliated, somewhat fibrous, light yellowish-green mineral resem- 

 bling picrolite, but which examination proves to be otherwise, as will be 

 noted later. 



The exterior of many of these nodules is strikingly like that of peb- 

 bles scarred by glacial action, and present other features such as to 

 suggest they have been subjected to a considerable compressive force. 

 When broken open the nodules are found, as a rule, not to consist of 

 serpentine throughout, but to contain a core or nucleus of a while or 

 gray mineral which, as above noted, has, on casual inspection only, 

 been mistaken for the ordinary dolomite of the quarry. There is no 



*Traus. Roy. Soc. of Cauada, vol. 1, also Mm. Physiology ami Physiography, p. 434. 



