188 ME. C. T. TEECHMANN ON A MASS OF ANHYDEITE [June 1913,. 



C. Tough, coarse-grained, highly gypsiferous "I 



limestone, darker in colour than B. The | Strophalosia lamellosa Gein. ; 



gypsum occurs in cracks and fissures, and Y in poor preservation, but clearly 

 is also lai-gelj r incorporated with the mass | recognizable. 1 



of the rock. j 



D. A verv dark, highly crystalline, but friable"! w ... . , . c , ,, . 



and porous limestone; much broken up in I J****?* elongata Schl & 

 parts. This is the broken limestone fBakevelha ceratophaga Schl. ; 

 whence the water was obtained. hoth fairl y numerous. 



1 I have since detected traces of bryozoa, and a small obscure gasteropod in this, 

 bed. 



The following analyses of the four samples were made, excluding 

 the gypsum and anhydrite, so far as it was possible to remove 

 these substances by hand before analysis : — 



A. A> B. a I). 



Insoluble residue 2 .' 2'03 278 O'27-l'OO 082 0'62 



Water, organic matter, etc. ... trace trace trace 3'17 2'29 



AI2O3, P0O5 trace trace Crlo trace 0'2O 



FeO 0-61 0-83 T56 f06 5-37 



CaC0 3 38-16 52-36 56-00 42"86 56"39 



MgCO.i 32-80 45-01 4279 33"92 34"97 



CaS0 4 27-40 — 0-18 19-04 1*17 



1 Calculated without the anhydrite which is disseminated through the rock. 



2 The insoluble residue of all these samples is very much alike, and offers the- 

 following peculiarities : — 



(1) Comparatively large quartz-grains: some with idiomorphic outlines, others 



irregular, and both full of inclusions. The inclusions consist of crystals and 

 crystal-aggregates and groups of pyrite, showing the cube, octahedron, and 

 pentagonal dodecahedron, mostly in combination one with the other. The 

 idiomorphic quartz-grains show clear margins, where the perfect crystal has 

 subsequently grown round a normal irregular grain with pyrite inclusions. 



(2) Free pji-ite in aggregates and free crystals of the above-mentioned forms and 



combinations. 



(3) Highly refractive grains resembling zircons with rounded angles. 



(4) Dichroic minerals resembling tourmaline in occasional crystals. 



Only in one limestone at the surface (concretionary series) have 

 I yet seen residues of quartz enclosing pyrite. 



The limestones obtained in this boring are unlike any member of 

 the series exposed at the surface. Their dark colour is largely due 

 to organic oily matter, but more especially to impure unoxidized 

 iron salts chiefly present as ferrous carbonate. The highly mag- 

 nesian character of all of them will be noticed, a feature indicating 

 the original state of deposit of the formation. 



Sample A, the rock interbedded with the anhydrite, is assumed,. 

 T think safely, to be a limestone, if not in the condition of deposition, 

 at least with its constituent elements present in the proportions in 

 which they were originally deposited. These samples are com- 

 pletely enclosed or encased in the bed of impervious anhydrite. The 

 rock is hard, dense, and compact, recalling in this respect any normal 

 Carboniferous or other limestone. It is entirely unbrecciated and 

 undisturbed. It contains a large quantity of anhydrite but no 

 trace of gypsum, the anhydrite being arranged in parts in plates 

 and aggregates of tabular formless crystals throughout the rock, 

 recalling, as will be shown, in appearance the hollow negative 



