Sand and Gravel
At risk of stating the obvious, your main options are:
1. Sell as is, marketing the property to aggregates companies.
2. Sell to an aggregates company "subject to planning". This allows the buyer to tie up your property for perhaps eighteen months (depending on what's agreed) and they will then probably be prepared to pay a higher price, as they only have to buy it if and when they get planning. You might get them to make the deposit, or part of it, non-refundable.
3. Apply for planning yourself and then sell as a "ready to go" quarry/sandpit site. This will yield the best price (IF, of course, you get planning). Of course, the planning process is expensive (includes an EIS) so you need anywhere from €30k-€150k in the bank before you can contemplate this.