There's never a shortage of losers in the stock market.

Let's take a closer look at five of this past week's biggest sinkers.

Company

Sep. 23

Weekly Loss

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SIGA Technologies (Nasdaq: SIGA)

$2.94

(43%)

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Keegan Resources (AMEX: KGN)

$5.34

(43%)

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Stillwater Mining (NYSE: SWC)

$8.59

(35%)

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Pacific Biosciences of California (Nasdaq: PACB)

$4.04

(33%)

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Cheniere Energy (AMEX: LNG)

$5.07

(31%)

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Source: Barron's.

SIGA was Nasdaq's biggest loser after a court ruled that it must split the profits on a promising smallpox drug with PharmAthene (AMEX: PIP). Then again, it was such a bad week for the market in general that PharamAthene -- after initially spiking on the news -- also lost ground on the week.

Miners were major casualties during a week that saw investors lose interest in precious metals. Vancouver-based gold miner Keegan and platinum and palladium specialist Stillwater were among the commodity sector's biggest sinkers.

Pacific Biosciences was more DOA than DNA last week after announcing layoffs that would reduce its payroll by 28%. Pacific Biosciences has a shot at revolutionizing the industry with its cost-effective genetic testing, but it obviously isn't doing so well if it feels the need to dramatically shave its overhead.

Finally, we have Cheniere, feeling the pain after revealing a strategic equity offering sales agreement with Miller Tabak that could result in the sale of up to 10 million shares. There's nothing fundamentally wrong with raising capital, but it's the wrong time to hit existing shareholders with the prospects of dilution.

It was a rough week for these five stocks. Let's see if they bounce back.