"Lepidolite" was actually discredited as a unique mineral species. It is rather a "catch-all" name describing purple or lilac colored Muscovites belonging to the solid solution group of Polylithionite - Trilithionite, which are lithium rich micas. Lepidolite is often found in LCT (lithium - cesium - tantalum) pegmatites and can often be enriched in rubidium.
This particular habit of Lepidolite is often described as "ball-peen" Lepidolite for its similarity to the ball-peen hammer. David London describes this habit in his book "Pegmatites" and again sites differential or rapid growth in the constantly evolving chemical environment.