﻿British Mineralogy. 327 



had previously been flattened out extremely thin on an anvil, it 

 became instantly coated with a firmly adherent film of chloride 

 of silver, which effectually protected it from the further action of 

 the acid; and it was only after repeatedly removing this film by 

 dissolving it off with ammonia, that the entire amount of gold 

 could be converted into the state of chloride. 



Two analyses were made, and afforded respectively the follow- 

 ing percentage results : — 



Gold 81-11 81-27 



Silver 18-45 18*47 



Silica (quartz) . . 044 Q-26 



100-00 10000 



From these numbers it will be seen that the composition dif- 

 fered very considerably from either the Clogau, Wicklow, or 

 Cornish gold previously examined, and that it was alloyed with 

 much more silver than even the stream-gold from the washings 

 in the river Mawddach near Dolgelly, which by analysis afforded 

 as much as 13-99 per cent, of silver. 



The associated minerals, as far as I have been able as yet to 

 verify, are : — quartz, which frequently is entangled in even the 

 very small particles of gold ; garnets, the iron alumina variety or 

 almandine, of a pale red or rather pink-red colour, often crystal- 

 lized in dodecahedrons and about the size of pins' heads ; mica, 

 iron glance, titanoferrite, magnetite, and iron pyrites. 



Upon washing the gold from the lighter substances, there in- 

 variably remains a quantity of black sandy particles mixed with 

 grains of quartz and garnets in fragments as well as in minute 

 rounded dodecahedrons : upon treating this with a magnet the 

 greater part of the black particles are removed ; but there remain 

 a number behind, which consist of black iron glance along with 

 apparently non-magnetic titanoferrite. The black particles taken 

 up by the magnet were examined and found to possess a specific 

 gravity of 5*08 at 60° F., and to give a blackish-grey streak. On 

 analysis they were proved to be composed of 





Oxide of iron . 



. . 91-26 



Titanic acid . . 



. . 8-03 



Silica . . . 



. . 0-71 



10000 



so that I imagine that the sand consists principally of grains of 

 magnetite along with a little Ilmenite, or some other variety of 

 titanoferrite. 



Although the native gold from Sutherlandshire has as yet only 

 been obtained from washing the alluvial deposits which have ac- 



