KiNAHAN — 0)1 Ingenite Bocks. 



181 



under a favourable light they are found to be irregular minute black 

 tubuli — some being straight, others curved, some oblique to or at right 

 angles to one another, while some are short and others long. At the 

 apex of the triangle there are a few air bubbles, but in the rest of it 

 only one was detected. 



The felspathic base, under a power of 386, shows a greenish-brown 

 ground, thickly covered over with whitish dots, lines, and broken 

 lines which are irregularly mixed up together ; while in many places 

 in it there are incipient forms, as if different minerals had attempted 

 to crystallize out. It is also found to be principally a mixture of two 

 felspars, one semi-opaque with irridescent spots, the other having a 

 parallel play of colours ; these seem to be most irregularly combined, 

 but the latter apparently predominates. 



The felspar crystals developed in the matrix seem, all to have ill- 

 defined margins. The most perfect seen in the slices is a twin crys- 

 tal (fig. 3). Of these the left-hand member has an imperfect ribaned 

 structure parallel to the long axis of the crystal ; while in the right- 

 hand crystal there is an obscure oblique structure. In all the crys- 

 tals of this felspar there are inlying opaque black specks, probably of 

 pyrite ; the large black speck figured near the bottom of the left-hand 

 crystal (fig. 3) seems to be a perfect hexahechon. 



Besides the more or less regular crystals of felspar, there are ir- 

 regular secretions, which consist in part of a semi-opaque irridescent 

 felspar («, fig. 6), containing, what seems to be nuclei, irregularly-shaped 

 masses, {h) of a felspar, in which is a play of colours in parallel lines, 

 similar to that displayed by a section of labradorite ; while scattered 

 about in the felspathic matrix are more or less well-formed small 

 crystals (<?), apparently of the same felspar as the first-mentioned 

 nucleus. 



Fig. 3. 



Fig. 4. 



Two of the nests of greenish flakes, when magnified to 33 dia- 

 meters, are figured (fig. 5). "With a power of 385, the uppeimost of 

 these nests is found to be fringed by flaky crystals of an olive-green 

 mineral, while the central portion is principally crystals of pyrite (?), 

 with which are associated the olive-green mineral. In the oblique 

 lower nest the olive-green mineral and the pyrite (?) are irregularly 



