108 



From other places in the world very little is recorded 

 about gyrolite; at Sundelaget in the Færoes, it is found M 

 with apophyllite superimposed and the same is the case with 

 the gyrolite from New Al maden, California'^), while it in 

 Nova Scotia^) is stated to be younger than the apophyllite. 



As a rule, however, we find that the succession of minerals 

 is the following. 



1. One of the zeolites: natrolite, mesolite, scolecite or thomsonite. 



2. Gyrolite. 



3. Apophyllite. 



This association seems very difficult, if not impossible, to 

 explain; it is highly surprising that the zeolites of the group 1 

 which contain the most alumina of all zeolites are found to- 

 gether with the gyrolite and the apophyllite which contain little 

 or no alumina while all the other zeolites very rarely occur 

 with them, further, the order of formation is very obvious 

 when we take into consideration the amount of lime in the 

 three groups; it is for the first group — 14 pCt., for the 

 gyrolite 30^ — 33 and for the apophyllite с 25 pCt. For the 

 sake of comparison I give the composition of the three groups 

 in the following scheme: 



The only constituents wich seem to be able to produce 

 that succession are the alumina wich is decreasing and the 



^) Cdrrie: 1. с p. 94. 



2) Clarke: Am. Journ. Sei. 38, 1898, p 128. 



3) How.: Am. Journ. Sei. 32, 1861, p. 13. 



