RE: Today's actionHere is an extract from a Bloomberg News article:
"First Majestic Silver Corp., which operates in Mexico, jumped 10 percent to C$16.77. The company will be added to the NYSE Arca Gold Miners Index on Dec. 19, Todd Anthony, investor- relations manager for First Majestic, said in a telephone interview. The index is used for the $8.65 billion Market Vectors Gold Miners ETF."
I think this explains the action.