Miss I.H.I — / i .355 



Me m the - and 



def:. - le minerals and the develop."-. 



in tli . 



3 The . • . t the roeke by weathei _- 



: mm logi Lteraf a the felspar was 



by ehl rite muscovite, qu... - .- 



in some ate. These altera! bow 



evidence of being developed before th< -^ere modi 



re tc which this area was subjected, and probablv at an e 1 

 ..... :beir history. 



A; a result of pressure the rocks became folded, faulted 1 1 ". 

 -- The veins were crumpled, strain shadc~ - — leveloped 

 in the quartz in the veins, amygdales were elongated and flattc 

 and felspar and augi:- rystala broken. The chl . I hea -..--. 



were elongated and lost any definite outline they may ;;. .. 

 have possessed. Very little mineral development seems to have 

 taken place at this stage of alteration. 



A further effect of mechanical deformat::^ is shown in ~ie 

 seoriaeeous basalt from Eaglewood quarry, which is dark purple 

 in col . - much cleaved: it passes into a purplish-re 1 slate 



with greenish and whitish patches on the cleavage surfaces. E: sks 

 of this character are common throughout the Hstrj t ind, no doubt, 

 many of them have originated in this way. although ne ... e: 

 exposure than the one quoted showed proof of this. 



The last stage of decomposition is that caused by weathering 

 agencies which split up decomposed rocks along the cleavage planes 

 and oxidize the irony material to minute grains of limonite and 

 hsematite. giving the characteristic red and brown colour t: the soil 

 and much leeomposed rocks. 



- Fragmental Rocks. 



A certain number of undoubted fragmental rocks can be identified 

 in this area, although many of the much altered rocks cannc: be 

 definitely determined as clastic or igneous. The undoubted 

 fragmental rocks differ in coarseness, but the recognizable fragments 

 in all cases are mainly \i felspar. In addition, some of the tuffs 

 contain rock fragments and remains of basic lapDU 



The felspars are often broken and always decomposed. In the 



: b of the tuff collected from the quarry behind Crowdy's corn mill 

 XXIX , the felspars could be identified as oiigoclase. Aggregate e 

 of crystalline calcite are often abundant in the tuffs, and as a rule 

 no organic structure is traceable ; but in the ash from this quarrv 

 one of the calcite patches showed distinctly the typical structure of 

 a fragment of an echinoderm. 



Lapilli do not occur in the specimens collected from the m un 

 Ashprington area, but are shown in a section from a loose specimen 

 found on a hill near Eight Acre Pen?, Einhay. This is the locality 

 referred to in the Torquay llemoir p. 73' as occupied by a eoai 

 volcanic tuff surrounding a probable volcanic neck. The outlines :: 

 the lapilli, which are roughly elliptical, have become very indisl ... ( 

 In them the groundmass is a colourle?- levitrine I .. --. and cont. 



