It is possible to treat natural clear quartz (and occasionally other suitable minerals, such as danburite) in a process that bonds atoms of precious metals to the exterior / matrix of the crystal. These crystals are very usable in crystal healing and meditation etc - their uses vary widely according to their nature (more about them below). The colour of these enhanced crystals vary depending on the metals used in the process; and have an energy that, unlike 'dyed' crystals, add to and extend the usual attributes of the base material - a word of warning here, some 'aura' crystals on the market ARE dyed, or have undergone a cheaper process that skimps on the materials: the best aura quartz is never cheap!
FLAME AURA - (and see moon-shadow aura, heart-flame aura and midnight sun aura): is treated with titanium and niobium, resulting in the crystals having a rainbow coloured appearance, with shades of gold, magenta, green and aqua-blue being prominent. This is quite a forceful stone with a vibrancy and power that is very 'awakening' and energising. Titanium is a great connector, and as such this crystal has great uses in journeying and connecting with Higher Guidance through meditation. It also carries the Rainbow Rays, which can help balance and charge each energy centre and indeed the auric field - try laying in a 'Star of David' grid of 6 of these crystals, preferably double-terminated, otherwise points-in.
AQUA AURA: is treated with gold, resulting in the crystals having a rich aquamarine colour with subtle rainbow flashes. This was one of the first treated minerals to be created, and is probably the most useful for healing purposes. This is a gentle but profound crystal, very useful when used to strengthen, clear and balance the communication centres (throat and brow) and to enhance and support communication of all sorts, whether this be verbal, written or telepathic. This is also a great stone for encouraging Angelic connections. The gold aspect also makes this an excellent crystal for working with any problems where the nervous system, cellular structure or DNA is in need of repair or adjustment.
OPAL AURA (also known as Angel Aura or Rainbow Aura): is treated with platinum, silver and other trace minerals, resulting in the crystals having a pearlescent white colour with an iridescent finish. This crystal has a sweet, fine and high resonance, which seems to sing in the hand. It carries the Rays of the Divine Feminine and of Cosmic Enlightenment, and is a very 'connecting' stone. If you wish to extend or activate your upper chakras, whilst retaining a sense of peace and serenity, then this is an excellent crystal to work with. It also brings in the full spectrum of Light, which can help purify and cleanse any of the energy bodies or centres whilst strengthening purpose and resolve.
COBALT AURA: is treated with cobalt, resulting in the crystals having a deep indigo, cobalt blue, magenta and gold colouring. Sometimes this crystal is mistakenly confused with Flame Aura. This crystal shouts 'Archaeon Michael' to me, with its deep blues and golds! Strong, protective, reflective and supportive, this is an ideal crystal to carry or wear for protection against unwanted negative influences or psychic attack. It will also support the upper chakras and provide protection and energy whilst channelling, journeying or communicating with Guides.
TANZINE AURA: is treated with gold and iridium, resulting in the crystals having a light indigo-blue /violet colour with an iridescent finish. Similar uses as for aqua aura apply, but with enhanced clarification and expansion of the crown chakra, supporting greater contact with the energies of the upper chakras (8-14) and the Higher Self.
CELESTIAL AURA: is a mix of aqua aura and opal aura, and combines their attributes in a wonderful stone that resounds with a high and fine energy. These rare stones were created in error (!) when a set of tumbled stones were inadvertently treated twice. The Divine Feminine and the Silver Ray are strongly grounded through this stone, together with the Pure Ray of Truth.
RUBY AURAis treated with platinum and gold to produce a colour that is very like 'Cranberry glass', which was popular in Edwardian times. It is highly energising and strengthening, with many of the qualities of the ruby, but with a directness that only permits that energy and strength to be used for the Highest good of yourself, and/or others. This is an excellent stone for initiating or catalysing change, and for self-empowerment if you have become down-trodden or lost.