212 THE PENOKEE IRON-BEARING SERIES. 



the shape of single crystals, or groups of crystals, of moderately large size, 

 and partly in the irregular, oval, opaque bunches of crystals above men- 

 tioned. The outlines of the single crystals are usually very sharply 

 defined, scpiare, hexagonal, and rhombic outlines })resenting themselves 

 constantly. On the whole the rhombic outline is the most conmion. In 

 the most regularly slaty phases of the actinolitic schists the iron oxides are 

 found to be aggregated much more ])lentifully in certain bands than in 

 others, the individual lamina" of these slaty rocks presenting in turn each of 

 the three main constituents as the predominant one. PI. xxviii, Fig. 4, 

 shows the arrangement of the minerals in one of the more ([uartzose lamiufe 

 of such a slaty rock, while PI. xxiii. Figs. 3 and 4, from ])hotographs, show, 

 with a much smaller degree of enlargement, portions of three laminae, the 

 central one composed mainly of quartz and actinolite, while the other two 

 are richer in magnetite, l)ut tliese last two iigures represent liy no means a 

 highly magnetitic phase. The rocks of the second or ferruginous chert 

 type have been described as presenting very commonly a most singular 

 occurrence of the oxides of iron, the particles of these oxides being distrib- 

 uted iipon the quartz background in, rude circles or ovals, or in two or 

 more concentric circles or ovals. In these cases the curving lines, made 

 up of particles of one or more of tlie three oxides, present no relation 

 whatever to the silica individiuils, traversing a number of these indi- 

 viduals indifferently, and looking as though j)ainted upon the silica 

 background. While this occurrence is far more common among the 

 cherty rocks of the second type, it is also met with among some of the 

 highly actinolitic slates, in which case the actinolite is usually associated 

 with the curving lines of iron oxide. In some cases actinolite and mag- 

 netite are associated in a bunch}' fa.shit)n, as, for instance, in PI. xxiv, 

 Fig. 2, and are at times dissevered from one another by the intru- 

 sion of silica, this silica, however, presenting the appearance of j)assing 

 about the several detached areas where these are sufficiently trans- 

 lucent to allow such a relation to be seen. These relations are still better 

 shown l)y certain rocks from tlie Animikie series. (Pi. xxix. Fig. 2.) The 

 existence of this peculiar structure in the highly actinolitic rocks is of very 

 considerable interest, since it furnishes one more link between them and 



