Despite a weakening dollar, gold and silver prices plunged sharply Tuesday -- breaking below key price support levels -- as lawmakers failed to make progress over resolving the fiscal cliff. Spot gold prices fell 1.19% to $1,696.60 an ounce. SPDR Gold Shares (GLD), tracking a 10th of an ounce of bullion, gapped down 1.10% to 164.30, a four-week low, in heavy volume. GLD failed to break above its key 50-day line, which is very bearish. The next level