The Sensex opened with a positive gap of 58 points at 13,107, and touched a high of 13,146 in early trades. The index, however, could not hold gains, and the selling gained momentum in noon trades with cement stocks cracking following the news that cement makers have agreed with Commerce Minister Kamal Nath to freeze prices at the current levels for one year. The Sensex tumbled to a low of 12,788 - down 358 points from the day's high. Buying at lower levels saw the index recoup some loss and finally close with a loss of 164 points at 12,885. The FMCG index shed 1.6% to 1689, and the Auto index slipped 1.3% to 4844. The IT and Oil & Gas indices were down 1% each to 4974 and 6118, respectively.The market breadth was negative - out of 2,466 stocks traded, 1,308 declined, 1,098 advanced and 60 were unchanged today.SLIDING STOCKS...Cement stocks were hammered once again today. Grasim slumped 7.5% (Rs 166) to Rs 2,069. ACC tumbled over 6% to Rs 781, and Gujarat Ambuja shed 2.6% to Rs 110.India Cements plunged over 8% to Rs 153, and UltraTech Cement crashed 4.8% to Rs 780.BHEL and ITC dropped around 3.5% each to Rs 2,095 and Rs 154, respectively. Cipla and Hindalco tumbled over 3% each to Rs 229 and Rs 128, respectively.Reliance Communications, Larsen & Toubro and Dr.Reddy's declined 2.5% each to Rs 423, Rs 1,482 and Rs 660, respectively. Reliance Energy, Wipro and Tata Motors were down around 2% each at Rs 480, Rs 565 and Rs 756, respectively.NTPC and Hero Honda rallied over 2.5% each to Rs 140 and Rs 690, respectively. Tata Steel gained 1.5% at Rs 434.IDEA SIZZLESIdea debuted on the BSE with a 23% premium at Rs 92 as against the issue price of Rs 75. The stock touched a high of Rs 94, and a low of Rs 84, before settling at Rs 85.55 - up 14% on Day 1.MOST ACTIVE COUNTERSDebutant Idea Cellular topped the value chart with a turnover of Rs 559.20 crore followed by Century Textiles (Rs 176 crore), MindTree (Rs 140 crore), ACC (Rs 135.25 crore) and Reliance (Rs 130 crore).Idea also led the volume chart with trades of around 6.36 crore shares followed by IFCI (1.26 crore), Gujarat Ambuja (75 lakh), Mudra (71.18 lakh) and India Cements (53 lakh).