Amethyst shards grow only on amethyst buds which are a block you can neither harvest nor move. I found a cluster of >32 just steps from a waste spawn. SMP7 Waste NW Go down the west stairs Go down the ladder at the bottom of the stairs. Great place if you need to grow crystals. But please don't break the blocks. You can't take them anyways since they break into nothing when mined. Just break the crystals when they're fully grown. They grow back on their own so you don't need to replant or anything.
It might be worth putting signs or torches on the blocks to protect them from being broken. It’s not hard to accidentally break it
Not from the sides you put the torches on, but on all the other sides, yes. It's worth it though to protect the farm IMO
note for anyone using the room: if you pick a non-fully-grown bud and you place it back, use /npmode or people won't be able to harvest it. There are already 3 clusters locked in this way