The only effects I've actually seen have been amber, which secretes an oil that can prevent teething pains, and bricks, being great for causing physical damage to any unwanted guests.
The crystals are useful for fantasy. For example, mana can be infused into the crystals as reserves. As for the emerald, it can be used as an accessory
The crystal themselves cant heal people, theyre just the vessels. Its the magical substance inside them like Mana, Ether, Holy energy, Qi, etc. That could supossedly heal people.
But those were only in fiction.
In real life, theres no such thing as healing crystal.
The closest thing to magical crystal is radioactive infected stone, which could damage you permanently instead of healing.
Never heard of a healing crystal IRL. Heard of time crystals, scrying crystals, and JO crystals, but that's about it.
Though I suppose if you google "metaphysical" and a gem of some sort, in this case emerald, you'll probably find most have healing on one site or another.