4.412. 



24 Dr Anderson's Analt/sis of Caporcianite and Phakolite. 



Phakolite, ■which, in its relations before the blowpipe, agrees in all 

 respects with the other zeolites, was analyzed after the foregoing method, 

 with this exception, that the quantity of water was determined simply by 

 the loss of weight sustained at a red heat. The composition was found 

 to be as follows : — 



Silicic acid, . 45.628 oxygen contained 23.703. 



Alumina, . 19.480 9.097 "| 



Peroxide of iron, 0.431 0.144 j ^•^"'' 



Lime, . 13.304 3.737 



Magnesia, . 0.143 0.053 



Potassa, . 1.314 0.222 / 



Soda, . 1.684 0.430/ 



Water, . 17-976 15.982. 



99.960 

 This constitution has little resemblance to that of chabasie ; for the 

 quantities of oxygen in r, A S and A q, are to each other in chabasie, 

 whose mineralogical formula is »• S'^ + 3 A S^ + G A q, as 1 : 3 : 8 : 6, 

 "whereas those quantities in phakolite are in the relation of 1 : 2 : 6 : Z^. 

 If we assume that the quantity of water has come out too high, which is 

 generally the case when it is determined by the simple loss of weight at 

 a red heat, then the constitution of phakolite would be represented by 

 the mineralogical formula >• S'' + 2 A S + 3 A 7, which transformed to 

 the chemical, is 3 r Si + 2 kl Si + 9 H. 



It appears, then, that phakolite belongs to that class of minerals which 

 in the first term contain a tersilicate, and in the second, a simple silicate 

 of the base, along with water. The minerals belonging to this class at 

 present made out are : — 



Gigantolite, . rS'+ AS+ A? r = /«, »m^, K.N. 



Hai-ringtonite, 1 „, . „ f >• = C.N. 



Mesotype, } ^ «' + ^ « "^ ^ ^ U'- = N.C. 



Lehuntite, . rS'-l- AS + 3A-/ »■ = (N.)C. 



Phakolite, . r S^ + 2 A S + 3 A ? /• = (C.)K.N. 



Mezolite, ^ . „, „.„ o. fr=N + 2C. 



c, , .. } J-S3 + 3 AS + 3 Aj { ^ 



Scoleziie, J . \r = G. 



Pyrargillite, . r S' + 3 A S + 4 A ? r — fe, mg, K.N. 



Antrimolite, . rS' + 5AS + 5A? r— C.(K.) 

 From this table it will be seen that phakolite forms a middle term be- 

 tween lehuntite and mezolite, and differs from them only in the second 

 or alumina term, which in the three minerals stand co each other in the 

 ratio of 1, 2, and 3, while the quantities of silicate of the monatomic 

 bases and water are the same in all three. 



