SECONDARY PRECIPITATION OF GOLD 259 
Colorado says, “The leaf gold is in exceedingly irregular masses, 
many of which consist of thin septa meeting at angles that strongly 
suggest deposition controlled in part by the cleavage planes of a 
rhombohedral carbonate of the calcite group. .. . . The [wire] 
gold does not occur in the clean, bright condition familiar in cabinet 
Fic. 2.—Gold replacing iron carbonate. XX 2 
Fic. 3.—Gold replacing iron carbonate. X 2 
specimens, but is imbedded in a reddish, earthy matrix, consisting 
largely of limonite, with oxides and carbonates of copper and 
various earthy impurities.” 
No doubt iron-bearing calcite can cause a similar precipitation, 
providing the iron is in the ferrous state of oxidation. Calcite 
is, of course, much more abundant than siderite in most gold 
