What does it mean when k is harder to crush up?

For context ive done a lot of ket over these past few months and each time, crushing the k hasnt been much of a problem, but this recent time it was much harder to crush. I usually just crush it up in the baggie using something hard and round and then put it onto a flat surface and crush some more using a credit card and it usually works. However this time i could only get it to look like chunks of salt. I was just wondering if it means that the k isnt as pure or something.