Theo (reply w/o spam) schreef
I cut some attractive slices out of a cedar that was being pruned, and
stuck them in a bag to dry slowly. (I assumed, correctly, that this wood was
unlikely to rot or be damaged by bugs on damp storage.) A couple of years
later, they were covered with a fur of beautiful needle-shaped crystals
with little smell or taste.

Any idea what these crystals might be?

+ + +
I have seen them too. Likely they occur in all Cupressaceae with heartwood.
Never got round to looking up what they might be. A quick look in Hausen
yields quinones &al as common in such woods, but this is an indication only.

PvR