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* FTSE 100 down 0.1 pct, mid caps down 0.4 pct
* Precious metals rise as safe havens in demand
* Financials biggest weight
* Acacia drops on Tanzania troubles
LONDON, Sept 4 (Reuters) - Britain's top share index slipped on Monday, breaking a three-day winning streak as rising geopolitical tensions sparked a broader sell-off in risky assets, with banking stocks hit the hardest.
Britain's blue chip FTSE 100 index was down 0.1 percent at 7,431.49 points by 0858 GMT, while mid caps fell 0.4 percent.
Shares in precious metals miners Randgold Resources and Fresnillo were the top risers, both up around 1.8 percent as underlying gold prices climbed to their highest level in nearly a year after North Korea carried out its sixth and most powerful nuclear test on Sunday.
Gold and silver miners are used as proxies for investing in gold, which is considered a safe haven asset in times of political and financial uncertainty.
"There is a thing called habituation. Markets are getting used to it, so whilst there is a bit of disquiet and there is a bit of noticeable reaction, I would suggest it is actually becoming more and more muted," Ken Odeluga, market analyst at City Index, said.
"Absent a significant escalation of rhetoric, maybe a significant escalation of the frequency, we are unlikely to see the markets really come off strongly."
Banks, however, took the most points off the FTSE 100 as shares in HSBC, Barclays and Standard Chartered dropped between 0.2 to 0.8 percent.
Banking stocks, which are more volatile than other sectors, tend to see their shares sold off more heavily when investors dump risky assets, and the broader FTSE 350 banking sector has lost 3.2 percent over the past month.
Analysts added that Friday's weaker-than-expected U.S. jobs report was also putting pressure on the sector, which benefits from higher interest rates, as expectations about another Federal Reserve rate hike this year had been dampened.
While individual moves were fairly muted among blue chips, shares in troubled mid cap Acacia Mining dropped 9.4 percent after it said that it would reduce its operations in Tanzania and cut jobs.
Acacia Mining shares are down more than 47 percent so far this year, hit by problems in Tanzania after it banned exports of gold and copper concentrate in March.
Shares in specialty chemicals firm Victrex rose 7.3 percent to a record high, however, after cutting its effective tax rate and confirming the appointment of a new CEO.
(Reporting by Kit Rees; Editing by Keith Weir)