Vol. 65.] PETROGRAPHY OF THE NEW RED SANDSTONE. 231 



II. The Minerals of the New Red Sandstone. 



The following is a list of the constituents, hitherto identified, 

 forming the finer material of the New Red Sandstone ; the minerals 

 are arranged according to their crystallographic systems: — 



(i) Cubic. 



(iij Tetragonal. 



Fluorspar. 



Anatase. 



Garnet. 



Cassiterite (?). 



Magnetite. 



Eutile. 





Zircon. 



(iii) Bhombohedral. 



(iv) Orthorhombic. 



Apatite. 



Bar'yte;?. 



Calcite. 



Brookite. 



Umenite. 



Celest ine. 



Hematite. 



Cordierite (?). 



Quartz. 



Sillimanite. 



Tuurmaline. 



Staurolite. 





Topaz. 



(v) Monoclinic. 



(vi) Triclin ic. 



Actinolite. 



Cyanite. 



Biotite. 



Microcline. 



Chlorite. 



Plagioclase- felspars. 



Muscovite. 





Orthoclase. 





Sphene. 





In addition to the simple mineral-grains, compound grains and 

 mineral -aggregates are common, including leucoxene, perthitic 

 intergrowths of felspar, serpentine, and micaceous decomposition- 

 products (presumably after some aluminous silicate, such as 

 cordierite, andalusite, or cyanite); grains of chert, felsite, micro- 

 pegmatite, and mica-schist are of frequent occurrence. 



Among the minerals acting as cements may be mentioned calcite, 

 limonite, haematite, barytes, celestine, and gypsum. 



It will be seen, on comparing the foregoing list with that given in 

 my previous paper, that the mineral species present in the New Red 

 Sandstone as a whole are, with a few exceptions, those already 

 noted from the Pebble-Bed. In the following description of certain 

 mineral species it is intended only to supplement the descriptions 

 already given. 



Those minerals which are now mentioned as occurring in New 

 Red sediments for the first time, or appear to call for treatment in 

 somewhat greater detail, are — anatase, calcite, haematite, quartz, 

 tourmaline, barytes and celestine, cordierite (?), staurolite, topaz, 

 actinolite, chlorite, and selenite. 



Anatase. — This mineral occurs in two distinct habits: 

 (a) tabular and (b) pyramidal. 



(a) The tabular variety consists usually of colourless or some- 

 times pale-yellow crystals, rarely exceeding 01 mm. in greatest 

 width. The basal plane (001) is large, and the pyramid-planes 

 {111} exceedingly narrow. The crystals are either single and 

 well formed, or are seen to consist of several crystals in parallel 



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