Sometimes, the lost desert wanderer does stumble into an oasis, replete with proverbial date palms and life-saving waters.

Most visions, though, turn out to be mirages.

And so it is with the latest bold announcement. Queensland Premier Annastacia Palaszczuk surfaced in Townsville on Tuesday to hear the company declare a "Final Investment Decision" has been approved on its Carmichael coal mine.

"Adani Project Gets Green Light", the Indian-owned miner declared in its press release and the media lemmings followed.

Indeed, "pre-construction work" on the Galilee Basin mine is to begin in the September quarter on a project that has so far cost the company $3.3 billion - including the Abbot Point coal port.

The Carmichael projects will generate 10,000 direct and indirect jobs, it says.

Interestingly, though, Adani omitted any number of the cost of the project. Is it $16.5 billion and Australia's biggest proposed coal mine, as so often?

A lot else is left unsaid, including the fact the mine has not received financial close.

Not so mega

That's why Downer EDI, one of the expected beneficiaries today only said it had received "further clarification of the scope of work to be done and the process for negotiating a binding mining services contract".

The Queensland government is keenly aware what is being proposed so far by Adani is not a "megamine", as treasurer Curtis Pitt noted last week. Carmichael "is certainly smaller than many mines around the world", Pitt said.

True, the $4 billion-odd mine being discussed in the Queensland cabinet might one day be expanded towards the original 60 million tonne a year monster that has fossil fuel fans drooling and environmentalists fuming.

But that "might" needs many unlikely factors to fall its way.

Can Adani get a $900 million loan from the federal government for a 400-km railway to link mine and port, for instance?

Can it get over remaining legal challenges, not to mention the protests from environmental groups determined to head off another giant source of greenhouse gases that will help cook what remains of the Great Barrier Reef, and all the tens of thousands of tourism jobs dependent on that?

"We have been challenged by activists in the courts, in inner city streets, and even outside banks that have not even been approached to finance the project," Gautam Adani, the company's chairman, intoned in Churchillian terms, omitting all but the beaches.

"We are still facing activists. But we are committed to this project."

Biggest hurdle

The highest hurdles, though, have always been thrown up by the investment and financial community. With Australian banks ruling out support, international investors are left to wonder what they know about the mine's viability.

Investment bank UBS's commodity team in 2013 viewed the project as a dud. It estimated a $A110 tonne thermal coal price as the "incentive price" needed for the Galilee Basin to be viable - a number repeated in the years since.

That sum compares with KPMG's forecast last month of Newcastle's benchmark coal trading below $US65 ($A87) a tonne for years to come - even before a discount is applied to Carmichael's typically poorer quality coal. (See KPMG's forecast Newcastle coal benchmark price chart below.)

It's not only that the coal price remains nowhere near what would make Galilee's lower quality coal profitable, especially when compared with Hunter Valley's exports.

But also that the whole "pit to plug" plan Adani was touting - digging, shipping, and burning its own coal - is looking increasingly dubious too.

Tim Buckley, a former Citi analyst and now director of the coal-sceptic Institute for Energy Economics & Financial Analysis, notes the news at home just gets worse for Adani.

Adani Power overnight declared on Monday it is considering selling control of one of its biggest coal-fired power stations mostly because it can't compete with imported coal. And India has vowed to ban imported coal within even  this year to save foreign exchange.

With Carmichael's prospects bad and getting worse, for Buckley the biggest question might be why Australian governments and the hopeful suppliers are being dragged along for the ride.

"What game are they playing, because Adani is not getting to financial close today," Buckley says.