200 



The remaining varieties examined by me contain, at least 

 somewhat more abundantly, ferro-magnesian minerals. As a 

 type I should choose the main rock in the large dike already 

 spoken of. It is a grey or, further inside the dike, a ruddy por- 

 phyry, with large reddish orthoclase crystals and numerous little 

 individuals of greenish-white plagioclase together with a dark 

 green mineral. The ground-mass itself rather retires, but the dike 

 in several places contains sections which are indistinguishable 

 from the main rock, except in that here the porphyritic cry- 

 stals recede, and possibly in their somewhat more basic con- 

 stitution. Under the microscope we see that both orthoclase 

 and plagioclase are considerably kaolinized; the orthoclase occurs 

 in large, not very numerous individuals, often as Carlsbad twins. 

 Phenocrysts of quartz, much corroded, only occur subordinately. 

 Sometimes we come across irregularly bordered areas of cal- 

 cite, which seem to fill up miarolitie cavities. Small crystals 

 of iron ore abound. The green mineral is entirely composed 

 of chlorite, and its appearance here seems to indicate that it 

 is pseudomorphous from biotite. The ground-mass is a not 

 especially well developed granophyre. 



From the same dike 1 examined a specimen of a divergent 

 appearance taken at the line of contact. Porphyritic felspar 

 (probably orthoclase, but strongly weathered) occurs only very 

 subordinately; the ground-mass is very compact and stands 

 midway between granophyre and felsophyre. In it occur nu- 

 merous thin laminae of chlorite, pseudo-morphs from biotite, 

 while on the other hand other large porphyritic individuals 

 consist of a serpentinic mass. They usually show rounded 

 outlines, at other times we find laths or vestiges of hexahedral 

 borders. The original mineral cannot have been mica; most 

 likely it was an amphibole mineral. 



While these contact facies occur rather isolated, we find, 

 among the blocks collected, many that correspond to the main 

 type. Orthoclase is never predominant, but always occurs in 



