i found these two entries...perhaps you can just apply it the way that is also specific to Amethyst.
http://www.crystalsandjewelry.com/crystalformations.html
"Cathedral Crystal (Castellated, Castle)
is recognized by a castle or cathedral like shape.
Properties Lore: Cathedral crystals (aka Castle or Castellated) are said to bring energies of balancing, uplifting, and to relieve depression, and anxiety. They are used psychically for astral travel, akashic wisdom, and travel to different "rooms" of the castle in meditation to access mystical knowledge you are currently ready to receive".
http://www.fortunecity.com/roswell/vanthal/21/infopics/c/cathedral.htm
"Cathedral Quartz crystals are named after their shape. They look like mini castles! The ones of the type shown above are not to be confused with Amethyst Geodes, these have only just started to be referred to Cathedrals in the last few years, where the crystals like the one shown above have been referred to Cathedrals for many decades.
Clear Cathedrals are referred to as Lightbrary Cathedrals. These crystals have doorways in them, more often than not, in their castling definition. To travel into the crystal, just gaze into the doorway, you will see it open and your consciousness will be drawn into the crystal. From there you can travel into different chambers and receive information that you are ready for at that time. You can also travel in inner and outer space in complete safety within the crytsal".
Deszroo