If a company representative comes to you with paperwork to sign, it could be for permission to undertake so-called 'minimum impact activity', or for more intensive exploration work. It may be difficult to determine the proposed scale of work at first glance.
Under the Crown Minerals Act, 'minimum impact activity' includes a variety of aerial and land surveying methods, taking small samples by hand or using low-impact machinery, and associated activities. It does not include the use of explosives, any more than minimal damage to vegetation or having more people on site than 'reasonably necessary'.
You may however be asked to allow more extensive activities. The important thing is to know what you're signing. The worst-case scenario would be signing something that you later find allows for larger-scale work that you were expecting, with associated disruption to farm activities, noise etc.
The key message is, do not sign anything unless your lawyer has had a chance to look it over. If you feel under pressure, simply ask them to come back at a more convenient time. And then get your lawyer on the phone.
You can also get free legal advice from the Federated Farmers hotline by phoning 0800 FARMING.