Key (aperture): Indentation/aperture on one or more sides of the crystal that narrows at it penetrates the crystal. These provide a doorway into unlocking parts of oneself that are typically hidden. Or, they can be used to access hidden information of any kind.
Meditating with one of these crystals can reveal what’s being hidden to you, especially by ones subconscious. A good tool to aid in letting go of things that hold your soul back.