264 DE. A. GILLIGAX OF THE PETROGBAPHY OF [vol. lxXV, 



The finer 'material or dust, caused by the pounding, and still 

 adhering to the grains, or present in large proportion in that which 

 had passed the 90 mesh, was removed by washing and decantation. 

 When it was deemed necessary, the material after washing was 

 treated with dilute hydrochloric acid to remove the iron oxides. 

 After washing and drying, some were mounted for examination 

 with the microscope in order that the character of the grains and 

 the relative abundance of the heavy minerals might be noted. 

 The separation was carried out with a Sollas bottle and Thoulet's 

 Solution of specific gravity 2*8. 



Heavy Minerals Present. 



Cubic System. 



Tetragonal. 



Garnet. 

 Iron Pyrites. 

 Magnetite. 



Anatase. 

 Rutile. 

 Zircon. 

 Xenotime. 



Hexagonal-Rhombohedral. 



Orthorhombic 



Calcite. 



Ilmenite. 



Tourmaline. 



Andalusite. 



Barytes. 



Brookite 





Topaz. 



Monoclinic. 



Triclinic. 



Monazite. 



None. 



In addition to these, the following minerals were joresent m 

 practically all the separations : — Leucoxene — as an alteration - 

 product of ilmenite ; small rounded grains of limonite and clay- 

 ironstone. Pyrolusite is often present as a cement in some of the 

 coarser beds, and the presence of manganese was proved in many 

 cases by chemical tests. 



Description of the Heav} r Minerals. 



Garnets. — These are by far the most abundant of the heavy 

 minerals in the coarser beds of the Kinderscout Grit and Rough 

 Rock. Some garnetiferous layers were found in the Rough Rock 

 of Cragg Hill Quarry, Horsforth, in which thej- occurred in such 

 quantity as to form the dominant mineral species. The}' are very 

 variable in size, the largest grains measuring as much as l'O to 

 1*5 mm. in diameter. The} r are generally of a rich pink colour, 

 but many of a deep wine-red colour also occur. 



In the garnetiferous layers they show evidence of having under- 

 gone alteration to some chloritoid substance by which they are 

 surrounded in pits, and the whole surface of the layer is deeply 

 stained with oxide of iron. Indeed, this characteristic pitted 

 appearance and colour of these layers has enabled me to collect 

 specimens from the heaps of broken rubble in the quarries. Where 

 the garnets are in contact with the large pebbles of quartz, the 

 quartz itself is pitted, which is due doubtless to some chemical 

 interaction between the garnet and the quartz. 



