Given the ongoing Knight Capital Group (NYSE: KCG) trading debacle which undoubtedly affected at least a handful of ETFs earlier this week on Wednesday and potentially yesterday as well, we have been prompted to examine some names closer given erratic trading in certain equity index components.

Thinly traded Market Vectors Rare Earth/Strategic Metals ETF (NYSEArca: REMX) averages about 87,000 shares on an average daily basis and is structured to deliver exposure to companies that are involved in the mining, refining, and manufacturing of rare earth/strategic metals.

With top holdings consisting of relatively unknown names including ILU (8.39%), LYC (7.95%), MCP (7.36%), KMR (7.28%), and TIE (6.60%), MCP was in fact one of the “affected” names from this Wednesday where the stock inexplicably went into a free-fall, dropping from the $17s range, all the way down to $14.35 for no apparent reason early in the session.

Volume in the stock also registered multimonth highs.

REMX concentrates on owning companies that mine rare metals such as cerium, manganese, titanium, and tungsten, as opposed to more common base metals such as copper, and these metals often have applications in technologies including cell phones and flat screen televisions for instance.