Both are Level 5. Both are Common rarity treasures. Both sell for 2 gold. Do we need two Named treasures that functionally do the exact same thing? No, we do not. The suggestion: Sell Amethyst shards for 3(or 4..?) gold. (they sound more valuable...)
We don't need any treasure at all - they could just give us gold, but if it's in there we might as well have some variety. There have been suggestions/speculation that treasures will form the backbone of a crafting system, so eventually they might be ingredients in different recipes.
The variety of treasures hearkens back to those random treasure tables in the old-school Dungeon Master's Guide, where you would roll to find out if the gems were lapis lazuli or topaz or whatnot. The players didn't care, they were just portable gold pieces, but it meant more chances for d100 rolls when you were setting up the dungeon.
