ORIGIN OF GOLD NUGGETS. 319 
Residue. Ag. Au. Cu. Fe. Total. 
1. Vein gold ...°02 5:16 9448 25 trace 99-91 
2. Alluvial gold ‘78 6°49 91°38 -09 by 98°74 
3. 3 she o504). Bb-16 re % 99°87 
4, - A ORO Rae to emma oF 93 99°62 
iL. Vein gold, Button’s reef, Marabastad, North Transvaal. 
2. Alluvial gold, Button’s Creek, derived from above. 
3. and 4. Alluvial gold, in flakes and grains. 
Hapervments. 
Freshly fractured pieces of the following sulphides were placed 
in cylinders of the photographer’s gold toning solution (fifteen 
grains of the double chloride of gold and sodium in fifteen ounces 
of water) viz., iron pyrites, molybdenite, mispickel, galena, copper 
pyrites, blende, argentite, dc. 
In some eases the sulphide reduced the gold at once and became 
gilt or coated with the reduced gold, either as a bright coherent 
‘deposit or else as a dull ochre-coloured one. Successive quantities 
of the gold solution were added from day to day as it became 
colourless, and in this way quite thick and strong deposits of gold 
were formed on the sulphides. 
In the case of the molybdenite, MoS,, the gold deposit was at 
first lustrous and metallic, but as time went on it became of a 
-dead brown aspect, although this under the microscope was seen 
to be made up of brilliant metallic points of light. Blue and 
white oxides of molybdenum separated out. 
The deposit on the mispickel was not compact and coherent 
dike that on the molybdenite, galena, and other minerals, but 
loose and easily rubbed off. 
The deposit on the iron pyrites was also bright and metallic 
looking at first but as it thickened it became dull and ochre-like 
‘In colour. 
The deposit on the galena was similar to the above; under the 
‘microscope, the surface, as in other cases, is seen to be minutely 
