Petrology of the Silurian Sediments. 45 



than tlie limonite impregnations, as they cut tlirough them in 

 jjlaces. The quartz veins crossing small cracks may have offered an 

 obstruction to subsequent iron-bearing solutions. 



No. 19 is a light-grey micaceous sandstone showing (juartz, mus- 

 covite, tourmaline, zircon, biotite, and oligoclase in a hne ground- 

 mass of quartz and sericite. Secondary minerals present are 

 limonite, sericite, and chlorite. This rock was obtained about twu 

 chains below No. 17 on the north side of the cutting. 



No. 20 is a yellowish loosely compacted micaceous sandstone 

 similar to No. 2 from Coburg. It was obtained about half 

 fi chain below No. 19. It shows quartz, niuscovite, tourmaline, 

 oligoclase, altered plagioclase, biotite, zircon, rutile. chalcedony 

 fragments, and possibly anatase. Secondary minerals are limonite, 

 leucoxene after ilmenite, sericite, and chlorite. 



No. 22 is a hard, porous, greyish-white quartzite, showing flakes 

 of muscovite. Microscopically it shows quartz, muscovite, tourma- 

 line, altered plagioclase, magnetite or ilmenite, zircon, leucoxene 

 after ilmenite, and rutile in a groundmass of fine quartz and 

 sericite. Secondary rutile occurs in very fine needles in cloudy 

 sericitic patches, possibly altered biotite. It was obtained from 

 a prominent bed six chains from No. 17 on tlie same side. 



ii., Studley Park Specimens. — No. 6 is a hard, compact sand- 

 stone traversed ])y secondary quartz and linu>nite veins. Tlie 

 section shows (|uartz — some Avith apatite inclusions — a very little 

 muscovite, zircon, rutile, tourmaline, magnetite or ilmenite, sphene, 

 and secondary sericite and limonite. The location of all Studley 

 Park specimens is shown on the sketch map (see below). 



No. 8 is a micaceous mudstone Avith grey and yellowish bands. 

 Microscopically it shows distinct current bedding. Minerals identi- 

 fied in the section include quartz, muscovite, and tourmaline, with 

 sec-ondary sericite and limonite. Some of the limonite is proba])ly 

 secondary after pyrite judging by its crystal outline. 



No. 10 is a Avhite mudstone from the crest of an anticline on the 

 river path, about a quarter of a mile N.W. of Johnston Street Bridge. 

 Microscopically it shows quartz, muscovite, biotite, chlorite, sericite, 

 and limonite. It is fairly even grained, Avith a fcAv larger frag- 

 ments of quartz here and there. 



No. 12 is a yelloAA'ish, hard, dense quartzite Avith secondary quartz 

 and limonite veins. Microscopically it shoAvs quartz, muscovite. 

 oligoclase, altered plagioclase, tourmaline — broAvn and grey — zircon, 

 cherty and sericitic intersticial matter, chlorite and limonite. 



