Sirius Minerals, the firm behind the £3.2bn polyhalite fertiliser mine near Whitby, is set to recommend the offer, but the news has been a major disappointment to thousands of Yorkshire investors, many of whom invested their pension pots in what they thought was a surefire winner.
No doubt there will be a blame game ahead and questions asked about institutions that blithely recommended buying the shares in what was always going to be a risky arena.
One mining analyst said it was a shame as shareholders had time to take some risk off the table and get out when the share price was over 30p.
Instead they are being offered 5.5p per Sirius share. While this is a premium of 34 per cent to the closing price of 4.1p on Tuesday, it is way below Sirius' previous share price.
Sirius' shares peaked at 45p in August 2016 and were as high as 37p in August 2018, but they have been on a downward spiral after the group failed to raise enough money to unlock the bank loans it needed to push ahead with the project.
The analyst said that in his opinion, the 5.5p per share £386m potential offer was "an absolute steal". He added that Sirius' management had done a "really good job, but they just couldn't get the final funding".
Unhappy shareholders now face two possible options if they don't want to back the Anglo American offer.
Almost half of the company’s shares are held by 85,000 small investors - an amazingly high percentage - so they could in theory block the deal.
This would be a risky move and Sirius' small shareholders lack a coherent body to represent them.
The analyst said: "If shareholders made a concerted effort, they could block the deal. Anglo needs 75 per cent for it to go ahead.
"However, 50 per cent of the vote lies with institutions and they might just want to get out. It's a real shame."
If shareholders do block the deal, the company could well become insolvent.
"It's Hobson's choice," said the analyst.
"They either get a smaller amount of money or take the risk they get none."
Another analyst pointed out that private shareholders do not have a great reputation for speaking out and voting at AGMs.
He said: "To mobilise 50 per cent of the shares would require all the retail shareholders to club together and vote against the offer."
He pointed out that some shareholders will have died, moved house or they may hold the stock through a third party platform such as AJ Bell. In the third situation, the platform will email shareholders, but many will not respond, miss the email or think it's spam and ignore it.
"My gut instinct is that the institutions will back it," said the analyst.
"They have lost a lot of money, but 5.5p is better than nothing."
The second option for reluctant shareholders is to hope that Anglo's bid flushes out a higher offer.
Both analysts said another offer is perfectly possible.
If there is another bidder out there, they will have to come forward pretty quickly as the talks between Anglo and Sirius sound like they are well advanced,
One analyst said possible bidders include BHP (formerly known as BHP Billiton), which already has potash interests, or perhaps a German or Canadian fertiliser or potash firm.
If another bidder doesn't emerge, shareholders probably need to accept that the 5.5p is the best they are going to get.
If there is a bright side to this story, it's that Anglo is focused on the broader benefits its bid will bring to the region.
It will put in the necessary finances, it has the expertise to run the mine successfully and it is committed to Yorkshire and to raising the employee numbers.
North Yorkshire is a region with a proud mining heritage and Anglo American is keen to develop this.
The last few months have been grim for Sirius shareholders. Unfortunately, small investors should never have thought it a wise move to put their entire pension pot into a venture that always carried great risk.
They also should have got out when the shares hit 45p, but that will be scant comfort for those who have lost out.