ORTHORHOMBIC AMPHIBOLES. 281 



replaced by sodium. The second stage in the process of alteration is the 

 beta-spodumene passing into eucryptite (hexagonal; sp. gr. 2.667) and albite 

 (triclinic; sp. gr. 2.62-2.65), or into muscovite (monoclinic; sp. gr. 2.76-3) 

 and albite, the uniform mixture of which has been known as cymatolite 

 (sp. gr. 2.69-2.70); or spodumene may pass into muscovite and microcline 

 (triclinic; sp. gr. 2.54-2.57). The reactions representing the above changes 

 may be expressed in the manner shown by the equations given below. 

 The change from spodumene to beta-spodumene may be written: 



(12) 4LiAlSi 2 6 +^C0 3 =2LiNaAl 2 SiA 2 +I^CO s +k. 



The increase in volume is 24.72 per cent. Where the beta-spodumene 

 breaks up into eucryptite and albite the reaction is: 



(IS) LiXaAl 2 Si 4 12 =LiAlSi0 4 +NaAlSi 3 8 +k. 



The increase in volume is 0.05 per cent. Where the beta-spodumene 

 passes into muscovite and albite the reaction is: 



(14) 6LiNaAl.,Si i 1 2+K2C03+2H 2 0+2C0 2 =2H 2 KAl 3 Si30 12 +6jS T aAlSi30 8 +3Li 2 C0 3 4-k. 



The decrease in volume is 0.76 per cent. In case the spoduniene changes 

 into muscovite and microcline the reaction is: 



(15) 12LiAlSi 2 6 +4K 2 C0 3 +2C0 2 +2H 2 0=2H 2 KA] 3 Si30 12 4-6KA]Si 3 8 +6Li 2 C03+k. 



The increase in volume is 31.74 per cent. 



One would expect reactions (12) and (15) to take place in the zone of 

 katamorphism, but I know of no observations on this point, nor as to the 

 conditions under which reactions (13) and (14) occur. 



AMPHIBOLE GROUP. 



ORTHORHOMBIC AMPHIBOLES. 



AXTHOPHYI.L1TE AXD UKDKITE. 



Anthophyllite: 



(MgFe)Si0 3 Mg:Fe::4:l, 3:1, etc. 



Orthorhombic. 



Sp. gr. 3.1-3.2. 

 Gedrite: 



(MgFe ) 2 Si 2 6 . MgAl 2 Si0 6 . 



Orthorhombic. 



Sp. gr. 3.1-3.2. 



-Anthophyllite and gedrite occur in the schists and gneisses, 

 both those derived from sedimentary and those derived from igneous rocks. 



