Two junior mining companies spent most of their first day of trading on the Australian Stock Exchange in negative territory yesterday, despite a bumper day for the sharemarket.

The benchmark S&P/ASX 200 Index rose more than 2 per cent yesterday but tungsten, molybdenum and uranium explorer Thor Mining finished 10 per cent below its 20¢ issue price, while gold and base metals explorer Shield Mining spent most of the session below its 20¢ issue price, but was pushed up to 21¢ in the last 15 minutes of trading.