The item name is Crystal.
It is classified as a gem, and is bought for 100 gold (75 with discount, and sells for 20).
The description is "Is this crystal a source of healing and energy, or just a pile of mumbo jumbo? You decide..."
That item is a gem, used in enchantments. It has no actual healing properties, and that description (that mentions healing) is just flavor text, without any actual meaning or function besides just...flavor. Specifically, they are used in all Fire Curse enchantments (for weapons).
There is no "Healing Crystal" item. There's a Healing Orb, in FoV, but it is a quest item, and can only be used for its specific quest.