The share market is lower for a fourth straight day as further falls in iron ore prices drags on the big miners.

IG market strategist Evan Lucas said the lower iron ore price was the main culprit behind the market fall, as it had been for last three weeks, in which the market has lost about 3.6 per cent in value.

Fortescue Metals, Rio Tinto and BHP Billiton were all being hit hard as iron ore prices dropped to $US70 a tonne for the first time in five years.

BHP Billiton was down 57 cents at $32.10, Rio Tinto had dropped $1.19 to $56.79 and Fortescue Metals was nine cents lower at $2.65.

Investors are concerned China’s cooling property market could continue to affect demand for iron ore.

“That’s why the materials space remains the one to watch – probably one of the worst performing plays around,” Mr Lucas said.

The major banks were experiencing some stability after falling in the wake of trading ex-dividend.

Commonwealth Bank was up 10 cents at $80.64, ANZ was up 21 cents at $31.98, National Australia Bank was up 16 cents at $32.29, while Westpac was down five cents at $32.74.

Woolworths was 91 cents weaker at $31.35 as Caltex wound back its fuel network ties with the supermarket giant.

Sonic Healthcare had dropped $1.08, or 5.9 per cent, to $17.32 after the international pathology, imaging and medical centres operator cut its forecast for its underlying earnings this financial year.

KEY FACTS

* At 1205 AEDT on Thursday, the benchmark S&P/ASX200 index was down 23.3 points, or 0.43 per cent, at 5,345.5 points.

* The broader All Ordinaries index was down 22.9 points, or 0.43 per cent, at 5,329.6 points.

* The December share price index futures contract was 20 points lower at 5,355 points, with 11,371 contracts traded.

* National turnover was 663 million securities worth $1.5 billion.