What is a skarn in geology ?
Serpentinite : definition
The intrusion brings a certain number of chemical elements (Si, Al, Fe...), which combine with those of the carbonate rock to form a wide variety of minerals, in particular calcium silicates : this is the phenomenon of metasomatosis. The masses of skarns frequently include monomineral levels (garnetites for example), and can contain exploitable concentrations (Fe, Cu, Mo, W, etc...).
The word "skarn" is an old Swedish miner's oath, equivalent to the interjection "shit", which expresses the disappointment of the miner discovering waste rock instead of rich ore. A skarn often marks the edge of a mineralized zone and therefore its end ; although skarns can constitute important deposits today, they were not technically exploitable in ancient times.