A. II. Phillips— Some JVew Forms of Natrolite. 473 



prism and the two pinacoids with the unit prism as the domi- 

 nant form. Terminations are rare and very simple, as they are 

 formed by the unit pyramid almost exclusively. 



The chemical composition of the large crystals, as given in 

 the analysis below, is that of a normal natrolite with a small 

 amount of Na.,0 replaced with CaO. 



Si0 2 

 47-17 



Alo0 3 



26-84 



Fe.,0 3 

 •07 



CaO 

 •12 



MgO 

 •05 



Na 2 

 15'89 



KoO 



•02 



II oO 



9-58 



Total 

 99-74 



Crystal forms. 



Eighteen of the small crystals were measured and the fol- 

 lowing forms identified : J (010), a (100), 8(310), t(740),e(2L0), 

 m(110), n (120), r (130), g (Oil), D (101), p (111), z (331), s (551), 

 y (131), £(311), o(151), oc (511), 2(531). Of the above forms 

 the prisms e(210), r(130) and the two pyramids o (151) and 

 2(531) are new forms for natrolite. The orthographic drawing 

 represents approximately the development and general relations 

 of these new forms. 



In the prism zone, the unit prism m (110) predominates, with 

 the two pinacoids equally developed, next in importance ; while 

 the prism n(120) is a small face, though constant, as it was 

 found on 16 of the 18 crystals measured. The prism i (740) 

 was a very narrow face, represented on 5 crystals and 8(310) 

 was represented by equally narrow faces on 4 of the crystals 

 measured. 



The new prism <?(210) was found on 12 of the 18 crystals, 

 usually represented by narrow faces but equal in development 

 to either i or 8. The signals were from good to dull and indis- 

 tinct. In one instance the face was large and the reflections 



