It was the rock that secured a company’s financial health but the legendary Gem of Tanzania has lost its sparkle forever.

Wrekin Construction, a building company in Shropshire, was unusual in listing the huge uncut ruby as its main asset. That rare accounting practice proved unwise when the gem’s £11 million valuation, which once underpinned the firm’s finances, began to look like a fantasy.

Administrators desperate to raise revenue from the failed construction company were today trying to sell the stone not to international gem dealers and jewellery houses but to fans of new age crystals.

With experts estimating a sale value of around £100, police officers said they were considering a fraud investigation into the valuation of the rough-cut purple stone.

David Unwin, a Derbyshire businessman, acquired the gemstone as part of a 2007 land deal along with two valuation documents. It was only after Wrekin collapsed in May that it emerged this stone was the biggest asset in a company that once turned over £103 million per year.

According to an investigation by The Financial Times, however, the gem was traded for around £13,000 in 2002 and was previously valued at £300,000.

Marcus McCallum, a Hatton Garden gem dealer, claimed that even those relatively conservative figures were massively inflated.

“The Gem of Tanzania may not be worth the cost of the advert,” he said. “A two kilo lump of anyolite [a low-grade form of ruby] is probably worth about £100. A valuation of £11m would be utterly bonkers.”

Ernst and Young have included the gem in a lot of office equipment formerly belonging to Wrekin on an internet auction site. Other items in the fire sale included a telephone with caller ID, an almost new ergonomic office chair and a white laminated desk with a foot pedestal similar to those issued by health and safety departments across Britain.

After it was reportedly turned down by the major London auction houses, the sale of the 2.1kg gem will also be advertised in Rock ‘n’ Gem, a quarterly magazine that targets mineral collectors, gem hobbyists and advocates of crystal healing and gem therapy.

The advert for the sale of the ruby describes it as "loose hexagonal crystal rough with co-existent green/black crystal matrix on its sides, opaque reddish purple in colour".

Ian Best of Ernst & Young said, "The joint administrators are seeking to maximise realisations from the Gem of Tanzania for the benefit of the creditors. The Gem will be widely advertised in specialist publications by our agents GVA Grimley Limited and details of the sale have been circulated to all of Wrekin's creditors and appropriate media."

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