(jcologij of Mooi'oodac. * 95 



the hill being X. 60 deg. E. On walking south-westwards to- 

 wards the large qua;rr}% further search gave negative results. 

 The rocks of the quarry are in places much disturbed. On the 

 south-western face of the quarry a steep anticlinal fold is seen, 

 and towards the >s. end an abrupt change of strike to E. and \V., 

 and a dip to N. at 70 deg. is noticed, while at the «outh end, 

 where the beds are less disturbed, the strike is nearly N.E. and 

 S.W., and the dip X.W. at 80 deg. At the opposite or Xurth- 

 easi face of the quarry the strike was observed to be 

 N. -20 deg. E., and dip E. 20 deg. S. at 70 deg. Possibly the 

 rocks oi the quarry belong to the same series as those in which 

 the graptolites were found, as a continuance of the N. 20 deg. E. 

 strike would pass close to the graptolite localities. 



The Mktamuupiiic Rocks of the Mookooduc Quahky. 



The rocks consist of sandstones and slates. The sandstones, 

 some of which occur in fairly thick beds, show little visible 

 alteration excejjt that in places they are changed to quartzite. 

 The slates are, however, highly altered. Among the slates are 

 some with alternate dark and light laminae. On splitting a 

 specimen of laminated slate along a bedding plane, elongated 

 colourless prismatic crystals up to an inch in length were seen. 

 A fragment of one of these crystals examined under the micro- 

 scope shows the refractive index, polarization colours, and pink 

 to colourless jileochroism characteristic of andalusite. 



Thin sections of the slates show the occurrence of two types, 

 the one more, the other less altered. The less altered type is 

 a spotted slate (Sections 505a and 50&I?). Under the microscope 

 crypto-crystalline to micro-crystalline aggregates of a white mica- 

 ceous mineral are seen to form abundant lighter areas with sub- 

 rectangular boundaries, while the fine-grained groundmass con- 

 sists ui biotite, quartz, uniaxial white mica, hematite, limonite, 

 and some dark red-bruwn rutile crystals. 



The white uniaxial mica is possibly bleached biotite, since 

 some oi the larger cry.-tals have apparently unaltered brown 

 areas parallel to the cleavage traces, while hematite and limonite 

 surround the white mica in such a way as to suggest that th-* 

 iron lias been leached from biotite and deposited as oxide round the 



