Not a professional but I think you will find the screenings with the coarser chunks to be less effective as the larger chunks can't really dissolve and be utilized to the same extent as fines, Lime itself is usually almost a byproduct of a rock quarry and not that expensive, most of the cost is usually the cost of hauling and spreading and most quarries will have a quality test report sheet on their lime to let you know the contents of the product, for instance between two local quarries here, one has a lime that tests a lot higher for ag use then the other, a much purer and whiter crushed limestone where the other is more of a shale rock byproduct, which you would have to spread twice as much to get the same result. hope that makes sense
