FTSE hits 1-week low as miners and tech stocks slump

* Blue-chip FTSE 100 index down 1.6 pct

* BHP Billiton (NYSE: BBL - news) suffers copper writedowns

* ARM results roughly in-line, stock falls after Apple (Swiss: AAPL.SW - news) weakness

* easyJet surges on demand for beach holidays

By Alistair Smout and Atul Prakash

LONDON, July 22 (Reuters) - Britain's top share index dropped to a one-week low on Wednesday after a poorly received earnings report from Apple (NasdaqGS: AAPL - news) hit technology stocks and weaker metals prices and an update from BHP Billiton dragged down miners.

The mining index slid 4.7 percent, as metals prices fell sharply. Diversified miner Anglo American (LSE: AAL.L - news) fell 6 percent to a 13-year low.

"Basic resources stocks are being hammered by weak metals prices as there are question marks over metals demand from top consumer China. Discouraging company updates have also soured sentiment," Richard Hunter, head of equities at Hargreaves Lansdown Stockbrokers, said.

BHP Billiton slumped 5 percent after flagging a hit to its full-year underlying profit of up to $650 million, linked to writedowns in its copper business.

Gold producers also fell. Fresnillo (Other OTC: FNLPF - news) dropped 3.8 percent as gold prices hit a five-year trough, in renewed selling after their dramatic slide early this week.

Britain's blue-chip FTSE 100 index was down 1.6 percent at 6,661.87 points by 1228 GMT after falling to 6,653.39, the lowest level in more than a week.

Chip designer ARM was down 5.6 percent. Although it reported a pretax profit that was only slightly below expectations, it was knocked back after Apple's results late on Tuesday.

Apple, which uses ARM's processor designs in its iPads, iPhones and watches, missed expectations with its forecast for revenue, adding to concerns that the smartphone market is weakening.

Equipment rental company Ashtead fell 4.3 percent after a double-downgrade from Bank of America (Swiss: BAC.SW - news) /Merrill Lynch to "underperform", traders said.

Among risers, easyJet surged 3.8 percent after it said higher demand for beach holidays helped support revenues, but added that there was still uncertainty from the unstable economic and political situations in Greece and the Middle East.

"While management points to a still uncertain macro environment, traders are focusing on the positives of increased FY guidance via lower fuel costs, revenues per seat holding up better than expected and passenger numbers and load factors still climbing," Mike van Dulken, head of research at Accendo Markets, said. (Reporting by Alistair Smout; Editing by Toby Chopra and Susan Fenton)