248 NOTES ON A GRANITE CONTACT ZONE — ^MoINTOSH. 



the characteristic pseudo-hexagonal form and twinning in 

 segments and in included laminae. Irregular lenticular 

 forms also occur. In the cordierite are inclusions of carbon, 

 biotite, and quartz. These are remnants of the minerals 

 which furnished the material for the formation of the cord- 

 ierite and are consequently older than the containing mineral. 

 The inclusions are arranged in lines parallel to the cleavage 

 of the slate showing that the cordierite was formed after the 

 cleavage and was not influenced by the pressure. 



Within the area extending from the edge of the granite 

 into the contact zone for a few hundred j^ards is the rock 

 already referred to as being distinctive on account of the well 

 developed cr\^stals that appear in it. Here the influence of 

 the hot granitic mass was most intense, and hence the meta- 

 morphism most pronounced. In the rock in this part of the 

 belt are found the minerals already described as occurring in 

 the other part, and in addition, fine andalusite crystals (Fig. 2). 

 These last occur as clear prism forms with prismatic cleavage. 

 Where wedge shaped outlines are found, the extinction is in 

 the direction of the w^edge length, from edge to edge of the 

 prism. The refraction is higher than that of the cordierite, 

 the double refraction low^ In an occasional spot on a crj^stal, 

 the characteristic rose-red pleochroism is seen. Portions of 

 some of the crystals are clouded with inclusions, while other 

 parts are quite clear. All the other minerals of the rock form 

 inclusions in the andalusite, so that it appears to have been 

 the last to form. Its variety', chiastolite, occurs quite often 

 in the slides. The carbonaceous inclusions are arranged in 

 the cross section of the prism diagonally, the bulk of it occupj^- 

 ing the corners of the prism, paralleling in a rough waj' the 

 extinction of the crystal. 



The only contact metamorphism noticed in the siliceous 

 beds is the production of a few flakes of mica with perhaps a 

 trace of scapolite and sillimanite (Fig. 3). A crystal of 

 andalusite occurs in a slide from a small granite dyke that 



