Move over bonds and cash - precious rocks, avant-garde art and collectible cars are now gaining favour as "alternative" investments for some of the world's richest high net worth investors.

According to a London-based Datamonitor wealth investment analyst Susan Ellis, high net worth investors are taking advantage of uncertainty in global financial markets by investing in art and other tangibles.

"For the most defensive of investors there are still the safer investment options such as cash, deposits and government bonds," said Ellis.

"However there is still plenty of concern about the safety of banks, with the fear that individuals' claims on investments may not be honored," she said.

For high net worth individuals, investing in tangible assets such as art, gold bullion, jewelry and antiques and collectable cars is "the equivalent of putting money under the mattress".

The trend is particularly prevalent now as certain tangible assets continue to have bargain prices attached to the items.

For example, the fine art market declined as much as 35 per cent this year.

But as wealth investors see the increased attraction of collectable assets to safeguard their wealth, this is having a knock-on effect in the insurance industry which is witnessing climbing valuations.

"In the past year we've insured more than [$2 million] to [$12 million-plus] fine art, jewelry and car collections than in the previous year," said Jamie Kearney, ultra-high net worth underwriting manager for Chubb Insurance.