It's possible that the price of your property would remain the same, but it's also likely that the pool of potential buyers would be smaller, given that some buyers would not want to live next to mineral extraction operations. The smaller pool of buyers could mean that it would simply take longer to sell. From the point of view that "time is money" you might say that your value would therefore be lower.
It's also possible that the pool of prospects would be so low that it would take a radical price reduction to get your property sold.
I would urge you to attend each and every meeting regarding this changing of zone and be as informed and vocal as you need to be to make sure your interests are heard. Since generally abutters are the ones officially informed of these matters, you might also inform nearby property owners (who are not directly contiguous to the property) whose property value might also be affected. If the change in zone is bad for you, you'll need as many supporters as you can.