Psychic
These gemstones are thought to enhance certain psychic abilities, increase the effectiveness of spells, or be useful to practitioners of magic and esoteric science. In general, many of the blue or purple stones are thought to enhance psychic abilities, while the "eye" stones are thought to protect from curses/evil-eye. Some dark stones are thought to provide protection.

Amazonite : Companion to Tarot and I Ching readings.
Amethyst : Ancient Hebrews believed it could induce visions.
Angelite : Astral Travel and Telepathy.
Apatite : Thought to induce visions.
Azurite : Potent psychic enhancer.
Blue Aventurine : Male Shamanic Gemstone.
Blue Chalcedony : Ward off psychic attack. Protect from black magic.
Bulls Eye Agate : Vision Quest Stone.
Calcite : Psychic amplifier.
Cats Eye : Protect from evil eye/curses.
Chrysocolla : Improve psychic ability, prophetic dreaming and trances.
Coral : Increase intuition.
Crazy Lace Agate : Protect from the evil eye/curses.
Emerald : Thought to block spells.
Dumortierite : Aids in recalling past lives.
Fluorite : A "psychic protection" stone. Astral Projection.
Garnet : Help achieve astral projection.
Iolite : Major gemstone of 3rd eye/Shamanic Healing. Astral Projection.
Jade : Thought to trap ancestors spirits in the stone.
Jet : Protects and absorbs negative energy.
Kunzite : Protects from ill-intentioned spirits.
Kyanite : Intuition.
Labradorite : "Wizards Stone". Important for 3rd Eye. Intuition.
Lepidiolite : Ease the way for Astral Projection.
Malachite : Drinking from a malachite goblet gives ability to understand animals. Evil Eye.
Moldavite : Thought to open us up to messages from other dimensions.
Moonstone : Foretelling the future. The Third Eye.
Mother-of-Pearl : Improve intuition.
Obsidian : Used as a Divining Stone. Powerful psychic talisman.
Onyx : Protect from psychic attack.
Opal : Give the "Gift of Prophecy" to the pure of heart. Astral Projection.
Peridot : Protects against enchantment.
Peruvian Blue Opal : Improve astral projection. 3rd Eye..
Petrified Wood Agate : Helps to recall Past Lives
Pewter : Foretell Future on New Year's Eve.
Prehnite : Improve Prophetic abilities. Astral Projection.
Quartz (Rock Crystal) : Divine the Future and commune with Spirits.
Ruby : Guidance through dreams. Protection.
Ruby Zoisite : Enhance all psychic abilities. Enter trances.
Rutilated Quartz : Aid vision in Astral Projection.
Sapphire : Said to amplify a witches power.
Shell : Used as holders in religious ceremonies.
Silver : Important to Wiccans and those who worship the Moon Goddess. Also protects during spells..
Smoky Quartz : Skrying stone.
Snow Quartz : Improve concentration during Tarot Card readings.
Sodalite : Facilitate ESP, Intuition.
Sugilite : Increase Psychic Abilities. Protect from "Psychic Vampirism".
Tektites : Thought to help with past-life regression.
Tiger Iron : Protect from attack. Return ill-will to sender.
Clear Tourmaline : Attune to Higher Beings.
Tourmilated Quartz : Thought to facilitate Astral Projection.
Blue Zircon : Increase spirituality