494 C. Palache — Occurrence of Olivine. 



First discovered by Dr. E. Emmons and described by Dewey* 

 as crystals of steatite, they came later to be regarded as steatite 

 pseudomorphs after quartz. Emerson first assigned olivine as 

 the original mineral, basing the determination on measurements 

 of the crystals, and comparison with serpentine pseudomorphs 

 after olivine from Snarum, of similar size' and color. 



In this paper Mr. Roe describes the locality and the finding 

 by himself of all extant specimens of hampshirite so far as 

 known, and this locality agrees exactly with the one from which 

 our material comes. He gives analyses of the pseudomorphs 

 and of the meerschaum-like serpentine matrix made by E. E. 

 Nicholson : both correspond fairly well with ordinary analyses 

 of serpentine although somewhat low in water. To the ma- 

 trix serpentine is given the name hampdenite, hampshirite being 

 retained for the serpentine of the pseudomorphs ; both names 

 seem to the writer superfluous since no varietal distinction from 

 serpentine is established, and the name picrolite embraces 

 varieties of serpentine with the characters of the so-called 

 hampdenite. Large magnetite crystals showing dodecahedral 

 and octahedral planes were associated with the serpentine pseu- 

 domorphs. 



Mr. Parsons decribes the crystals, giving contact measure- 

 ments and sketches of a number of them, and pointing out the 

 close resemblance to humite which they present in form and 

 angles. He regards as strongly confirmatory of the derivation 

 of the crystals from humite the facts : (1) that minerals of the 

 humite group are abundant in other Massachusetts localitiesf 

 and at Tilly Foster Mine, N. Y., in the last case in somewhat 

 similar paragenesis : (2) that crystallized olivine in good-sized 

 crystals has never been found in the region : (3) that the size of 

 these pseudomorphs is altogether exceptional for olivine. 



In view of the discovery of olivine crystals close at hand as 

 described above, quite comparable in size with the pseudomorphs, 

 although not so perfect in form, the confirmatory facts given 

 by Parsons of course lose all weight. The agreement in 

 crystal measurements is, it is true, less satisfactory for olivine 

 than for humite, as the following table, taken from Parsons' 

 paper with the addition of the figures for olivine, shows : 



Humite Pseudomorphs 

 (measured) 



Olivine 



210 to 210 49° 40' £ 49°-50° 



110 to 110 



49 c 57' 



001 to 014 45 32 £ 46 £-4 7 



001 to 021 



49 33 



001 to 011 76 13 74 



001 to 041 



66 55 



001 to 103 55 44 55 



001 to 101 



51 33 



001 to 216 58 16 58 



001 to 111 



54 15 



* See Dana, System, 1892, p. 675. 

 f Mr Emerson informs us that the localities 

 from Chester, and of different geological age ; 



cited are manj 

 and association. 



- miles distant 



