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v.- " BIue=Metal " Limestone. 



The stone is a blue-black carbo-argillaoeous limestone, with 

 some chert, which occurs in thin seams or as small pellets 

 distributed through the limestone. The calcareous zone in the 

 slates is about 30 or 40 feet in thickness, in which the so- 

 called "blue metal" makes beds of stronger stone, varying; 

 from a few inches up to 10 or 14 feet in thickness. Its dark 

 colour is distinctive, and the outcrops are usually marked by 

 the presence of superficial travertine. The beds occur at in- 

 tervals along the foot-hills adjacent to Adelaide, not on a con- 

 tinuous or uniform line of strike, but in faulted fragments. 

 The main localities for their occurrence are as follows : — 



Glen Osmond Road. — The relationship which this belt of 

 impure limestone bears to the associated slates can be well 

 seen in outcrops near the Mountain Hut Hotel, on the Glen 

 Osmond Road. The beds are on tlie old road, about half a 

 mile higher up than the hotel, and cross the new road in a 

 north-west directioa, just above the sharp turn which has ob- 

 tained the name of the "Devil's Elbow." Here a large quarry 

 has been worked m the stone, the "blue metal" having a 

 thickness of about 14 feet, with a dip of 20° in a direction 20° 

 south of west. The strike carries the beds along the hillsiae, 

 and obliquely across the lower bend in the road, and beneath 

 the Mountain Hut Hotel. 



Mitcham. — What are probably the same beds occur in 

 the thick slates on the south side of the Brownhill Creek, 

 opposite the school on the public reserve. The main lime- 

 stone is here 12 feet thick, w4th several thinner beds of lime- 

 stone in the section. It has been quarried at several points. 

 Dip south-east at 25°. 



Br'at/monf. The "blue metal" limestone is well exposed 

 in Goldsack's quarries, near Beaumont, on the Burnside and 

 Glen Osmond Road. The quarry face shows about 40 feet 

 of stone, with 14 feet of "blue metal." The limestone layers 

 . are separated by laminated and calcareous slates, which are 

 greatly puckered and compressed into small angfular folds and 

 little overfolds in the direction of the dip, which is west, at 

 25° -30°. The crush has developed a phyllitic structure in the 

 slates. The beds curve around the north side of the hill and 

 across a small gully to the east, and slope upwards to near 

 the top of the ridge, where the dip is at a lower angle and 

 apparently directed to the eastwards. A little short of the 

 summit the limestone is cut off by a bar of quartzite (much 

 penetrated bv quartz), about 12 yards wide, and cuts across 

 the strike. This is apparently a fault rock. On the east side 

 of this quartzite, or fault rock, are grev slates. 



