Especially when considering that the purchase would be an asset...

Especially when considering that the purchase would be an asset that will have positive cashflows soon after the sale is made. They could certainly service a loan after starting the quarry up and you would think that with security granted over the quarry and other assets there wouldn't be too much risk from the lenders side.
Or they could be negotiating an offtake agreement to pay for some/all of the purchase. I agree that raising more equity would not be a cheap way to fund it unless they can do it at a premium.

Perhaps the delay on the sale of the quarry is due to final negotiations on a finance facility/offtake agreement being put in place. The classic 'subject to finance' clause.