The FTSE 100 is down 0.50% at 6,802.95.
Precious metals miner Fresnillo is leading the blue chip risers, up 4% at 911p.
It is followed by Sainsbury's, up 2.5% at 266.65p, as the supermarket chain prepares to update investors on Christmas sales on Wednesday.
British Gas-owner Centrica is the biggest faller, down 4.62% at 130.95p.
On the FTSE 250, Dunelm retains its place as Monday's largest gainer, up 11.24% at 643.75p, after sales rose over Christmas and it upgraded its interim profit forecast.
The FTSE 250 is up 0.92% at 17,960.36.