Thaumasite at West Pater son, N. J. 233 



cient to form four hydroxyls, as constitutional. The last two 

 molecules are, moreover, expelled at four separate temperatures, 

 indicating the existence of four hydroxyls which play different 

 parts or have different positions in the molecular structure. 

 It is evident also that the CaSiO,, CaC0 3 and CaS0 4 , together 

 with the water, are united in some way into a complex mole- 

 cule, and probably as suggested by Groth* in some way anal- 

 ogous to the combination of silicate and sulphate in the hauyne- 

 nosean group of minerals or of silicate and carbonate in can- 

 crinite. Regarding silica as the linking non-metallic element, 

 the following constitution may be suggested as a probable one : 



HO-Ca-0 0-C = 



O-Ca-OH 

 Si , 13 H 2 



/ \ O-Ca-OH 



HO °- S ^o 



The above may also be expressed as [(CaOH)CO,] [(CaOH)SO,] 

 [CaOH] HSiG 4 , 13 H 2 0. The formula agrees in a very satis- 

 factory manner with the results obtained in driving out the 

 water, for it demands four independent and different hydroxyl 

 molecules. 



Formulae may be written with four hydroxyls and with either 

 carbon or sulphur as the linking element, bat they do not seem 

 to the authors so probable as the one given above. 



The occurrence of thaumasite at Paterson is in the trap 

 which has been quarried for road material. It is associated 

 with heulandite, apophyllite, laumontite, pectolite, chabazite, 

 scolecite and natrolite, all of which are found at the locality 

 in beautiful crystals. Widman mentions the occurrence of 

 apophyllite with the thaumasite at Kjolland. The thaumasite 

 has crystallized later than the zeolites and occurs upon or sur- 

 rounding them. A considerable quantity of it was found. 



In closing the authors express their thanks to Messrs. Geo. 

 L. English & Co. of ISTew York for generously furnishing them 

 with material for the investigation. 



Mineral ogical-Petrographical Laboratory, 

 Sheffield Scientific School, February, 1896. 



* Tabellarische Uebersicht der Mineralien, p. 149, 1889. 



