I've spent roughly 4 times as long chopping as digging. I have 7 crystalline blackrock, after 4 full pack horse loads of lumber I had 2 brilliant amber, various wood (inclucing some frostwood!) switches, fungi, parasitic, switches and not a single crystal shard. In desperation I wondered if my Mel's hatchet was causing a problem. I went and fetched an axe. Less than 5 minutes later I got my first crystal shard. Coincidence? or does the fact that Mel's hatchet gives me a theoretical 105 lumberjacking cause a problem?