589 



the granites. Thus e. g. from a qiiartz-tourmaline-zone of 4 mm.'s 

 breadth, the amount of biotite tlirougli a very narrow transitional 

 zone may increase to a large percentage in a qnartz-biotite-zone 

 containing much tourmaline. 



At IYj cm. from the contact this percentage of tourmaline is still 

 considerable. The biotite is strongly pleochroic, from reddish-brown to 

 almost colourless; the tournnaline is found in small crystals in the 

 quartz-biotite-mixture, but for the greater part in larger crystals, 

 which enclose numerous grains of quartz and also small crystals of 

 garnet. This tourmaline with sieve-structure is sometimes idiomorphic 

 but most times shows irregular forms; in the former case we often 

 see flakes of biotite along the circumference of the crystal, from 

 which it is evident that they have more recently crystallised. The 

 garnet too is always idiomorphic with regard to biotite. In the 

 qiiartz-biotite-mixture lath-shaped sections of biotite are sometimes 

 rather numerous. 



At another place near the contact we see that a small percentage of 

 biotite in a mixture of larger tourmaline-crystals with sieve-structure, 

 quartz and small garnets, has but slightly increased over a distance 

 of 2 cm. Thei'efore the transitional zone to rocks containing luore 

 biotite is much broader there. • The biotite is again reddish-brown 

 and shows a strong pleochroism. 



The presence of pale-brown mica in a quartz-biotite-zone, separated 

 from the tourinaline by rocks bearing a quartz-muscovite-zone, has 

 already l)een mentioned ab()ve. 



If the quartz-tourmaline-zone does not exist, quartz-biotite hornfels 

 are found at the very contact of the granites. Tourmaline-quai'tz- 

 mixtures rich in garnet, and quartz-biotite-mixtures with tourmaline 

 and containing little garnet, sometimes occur in the same section, 

 both at the very contact. Sometimes, muscovite occurs in a small 

 quantity together with biotite, and the contacl-rock is sometimes 

 separated from the granite by a narrow quartz-zone with or without 

 muscovite. The tourmaline occurring in varying quantity forms small 

 as well as larger crystals with sieve-structure. Snu»ll spots of ore 

 occur in small quantity ; in parts which have more or less ellip- 

 tical forms and are free from tourmaline, the percentage of ore has 

 slightly increased. 



In a specimen of the western contact of the dyke-shaped intrusion, 

 the quartz-tourmaline zone does not occur, and a fine-granular mixture 

 of quartz, biotite and muscovite with rather many small idiomorphic 

 tourmaline-crystals is seen. It is sepai'ated from the granites by a 

 narrow zone of quartz. Some spots of ore occur in these rocks, very 



