Anglo American, pressured by investors after an abortive merger bid from rival Xstrata, could offload its zinc operations first in a fresh divestment drive that could raise $6 billion.

A disposal of building materials group Tarmac, however, which has been up for sale for several years, may depend on economic recovery taking hold, analysts and industry sources said.

The mining group said last week it was expanding its divestment program by putting four more businesses on the block as part of a wider restructuring.

The zinc business may be the first to go because zinc prices have recovered strongly and they're high quality assets. That's the expectation in the market, an industry source who asked not to be named told Reuters.

The price of zinc has nearly doubled this year, touching a 17-month high on Monday, and is on course for a 17.7 percent rise this month as it benefits from producer cutbacks and Chinese buying.

Anglo's zinc operations consist of the Skorpion mine in Namibia, the Lisheen mine in Ireland, and the 74 percent owned Black Mountain mine and Gamsberg project in South Africa.

The unit -- which UBS estimated was worth $700 million -- produced 340,500 tonnes of zinc in 2008 and posted earnings before interest, tax, depreciation and amortization (EBITDA) of $209 million.

A natural buyer would be South Africa's Exxaro Resources, which owns the remaining 26 percent of Black Mountain/ Gamsberg and whose zinc refinery processes some material from Skorpion, said analyst Kieran Daly at Investec Securities.

Exxaro, however, may also be looking to exit the zinc business and could team up with Anglo to sell both firms' assets as a package, he added.

TARMAC MAY NEED MORE TIME

Anglo has wanted to sell road materials maker Tarmac for several years but froze the process during the downturn.

Anglo was still in no hurry to unload assets and Tarmac will benefit from more time to gain a good price, the industry source added. Analysts estimate that Tarmac is worth around $3 billion.

Anglo is not going to rush into a fire sale, they have no need to do so since these are all good businesses in their own right, the source said.

Tarmac will benefit from a pick up in trading conditions in terms of the UK housebuilding sector, general construction and road building.

A recovery in debt markets could also be instrumental since Tarmac could well be attractive to private equity groups who would need to raise finance, the source added.

Buyout houses such as CVC, Doughty Hanson DOUHA.UL and TPG TPG.UL had previously been interested, a source close to the situation and media reports had said.

In 2007 when Anglo first put Tarmac up for sale, French cement giant Lafarge and Irish building materials group CRH both said they would consider an acquisition.

Swiss Holcim said at the time it would not bid for the business, but would consider buying parts of it.

One of Anglo's businesses up for sale -- steel fabricator Scaw Metals -- may end up being sold on the stock market, Investec's Daly said.

Anglo may get the best value for this business by listing it on the Johannesburg Stock Exchange. A listing of Scaw, 74 percent owned by Anglo, would provide a good exit for local investors, he added.

Another strategy could be to break up the firm, which has operations in South Africa, South America, Canada and Australia, Daly said.

Analysts have estimated Scaw was worth about $1 billion.

The other two units up for sale are Brazilian -- fertilizer maker Copebras and ferroniobium producer Catalao -- and were worth around $580 million each, analysts said.

The actual sale processes for some of the assets were not likely to begin until early next year since preliminary work was needed to separate the businesses from the Anglo group, the industry source said.

You need to shape each business so they are stand-alone businesses. That preparatory work has begun, but it's still early days, the source said.

(Editing by David Cowell)