Crystal

This article refers to and will discuss the various uses of both Pyrite and Siderite crystals. The only magical crystals on the show have been either pure white and quartz-like crystal in appearance or tinted with yellow and similar to citrine.

Classification
Only two names for the crystals have been used on Charmed to refer to the crystals, and rarely, as usually the girls would just say "I'll get the Crystals". The first heard was "Siderite crystals". This term was used in the episode "Sight Unseen" when Prue took a crystal to the club on her date, much to the sister's surprise at the time as she'd been overconcentrating on The Triad at the time. The sisters asked her what the crystal was for and she said it was a siderite crystal which would alert her if the trap she'd laid (explained further under the "charging" section) was tripped.

And for several seasons afterwards "Siderite" had been the assumed name of the crystals. However in "Witchstock" Penny Halliwell took out a box of pure white crystals and told everyone to set up a perimeter with them. She then asked Paige if she knew what they were for and she said:

"Yeah they're Pyrite crystals, they resonate a harmonic tone when exposed to evil, kind of like a demonic alarm system."

This led to confusion amongst fans over the naming of the crystals and two answers were proposed. Either the yellow crystal was the siderite one (especially since they were referring to that one at the time) and the other, white ones were the pyrite ones (like in Witchstock) or Pyrite crystals were looked exactly the same as one of the two forms of siderite crystals (i.e. a white version and a yellow version), similar to how sugar can be brown or white and the latter looks almost exactly like salt but actually has a different chemical composition. The latter theory is supported by the fact that Paige actually made a demonic alarm system later in the show for Wyatt and led fans to misinterpet the latter to be true. However, when Piper asks how the demonic alarm system works Paige says:

"Ehh, its pretty basic, I just enchanted a few Cowrie Shells"

And so the demonic alarm system actually wasn't related to the Pyrite crystals after all, despite the (unfortunate) wording. Nevertheless, this makes further sense as many times the "white crystals" which have been used to create the crystal cage and/or trap have glowed and resonated a harmonic tone when exposed to evil, for example, when Cole came near them in the charged crystal trap in "Sight Unseen" they glowed and resonated a harmonic tone before he stepped into them and they shot him down, the same happened for Troxa in this episode.

Hence it would appear that, given all the facts, Pyrite crystals are the white kind and Siderite crystals are the yellow ones, which Prue enchanted to alert her of evil. It is unknown, though, whether one could charge Siderite crystals as with Pyrite ones.

Charging
A witch may bless or "charge" a crystal magically. When five charged crytals are placed in a pentagram any demon or other evil being who steps into the pentagram will be immediately shot down by five bolts of lightning, one bolt fired from each crystal aiming at the being's neck until it dies. For this to work all five crystals must be in place within the trap, if even one is moved the lightning will stop, but if it is replaced while the demon is still inside it will restart again.

Another form of crystal, the Pyrite crystal, can be blessed to produce a harmonic tone when exposed to evil and is often used as a form of "demonic alarm system". ("Witchstock")

This idea was first used by the Charmed Ones in 2000, when Prue placed five charged crystals around the Book of Shadows (expecting Belthazor to come after it.) She had a sixth, enchanted crystal which resembled citrine, a orange to yellow form of quartz crystal, that she carried with her. She enchanted the crystal so that it would glow when the cage was activated. When Belthazor did enter the cage, the Book repelled itself out and away from Belthazor and electrocuted him by forming a collar of energy around his throat and knocking him out. The trap was also used on Troxa later. ("Sight Unseen"). The tactic was more often used merely to hold evil in place for questioning purposes.

If the being is not dead by the time the crystals expand all of their charged energy then they will start draining power from other sources to continue fueling the process. This happened when Troxa stepped into the trap. He was inside for so long that the crystals had to start draining the electrical energy from the Manor's connection to the national grid.

The Crystal Cage


When 4-5 crystals are set in an East-West orientation they form a magical cage of bright energy around a being that isolates them from the outside world and protects the trickster from being trapped. However, although the cage lets nothing out it does let some forms of magic in, such as Potions.

Later, when a handsome man, a creepy clown, and a chainsaw murderer came out of the Charmed Ones' dreams, they placed all three of them in cages of three crystals. The man and the clown disappeared when Piper and Paige came to terms with their dreams, but when Phoebe's dream got worse, two more chainsaw murderers appeared, and kicked two crystals out of the way, disabling the remaining cage. ("Sand Francisco Dreamin'")

When a Kazi demon attacked at the manor, after a bit of a fight Phoebe was able to place the crystals around him to trap him. Paige had prepared some substance she could throw at the cage, that would cause him pain whenever she did. She did several times, trying to get him to answer what the Kazi king had done with their whitelighter, Leo. When the Crone killed the Kazi King, the Kazi warrior vanquished inside the cage as well. ("Sense and Sense Ability")

A major use of the Crystal Cage was in the Seer's vision of the Source's death: the Charmed Ones trapped him in it and when he threw a fireball at them, it bounced off the cage and vanquished him. During the final battle with the Source, the sisters tried to trap him in the cage, but he used Paige's telekinetic orbing to break the cage and thus it was ineffective. ("Charmed and Dangerous")

Another major use of the cage is when the Charmed Ones vanquish Cole for the first time. Piper, Paige and Leo orb to Cole's apartment and start placing crystals in a circle around him to trap him after Piper blows him up. Cole reforms in the middle and throws Paige across the room before Piper blows him up again. Piper calls out for Phoebe as Leo heals Paige and Cole reforms again. Phoebe decides to side with her sisters and completes the cage after kissing Cole one last time. The Charmed Ones recite the Source Vanquishing Spell while Cole is trapped in the cage and vanquish him. Trapped in the cage, Cole is unable to stop them. ("Long Live The Queen")

Note: It's possible to say that anyone who was trapped in the crystal cage couldn't use any kind of Teleportation as Cole or the darklighter could easily get out of the cage, if that were the case.

Limitations of the Crystal Cage
Paige, believing darklighters to be after an innocent, summoned one to the attic in a prepared crystal cage as a trap as a means of interrogating him. He accurately told her it wasn't darklighters, but she later got distracted talking to Piper and he tried to move one of the crystals. It at first shocked him when he tried to get near it, but then he managed to fight through it to knock one out of sequence disabling the cage so he could fire an arrow at them. Paige then vanquished him using his own crossbow. ("Siren Song").

The Charmed Ones used it to temporarily hold back the Source when he attacked. Initially in the Seer's vision, Paige Matthews would have orbed the crystals around the Source, deflecting any of his attacks back at him. But he prepared for this by stealing her powers with the Hollow. Although they were able to manually place them around him, once the cage formed, he brought it down by orbing one of the crystals into his hand breaking the cage. ("Charmed and Dangerous")

After Barbas managed to steal Cole Turner's powers, and vied for the Source's throne, the Charmed Ones figured they could vanquish him the same way they vanquished the Source. So Phoebe astral projected (with the use of a tweaked version of the Mind Link Spell to Barbas, luring him to the manor, where they trapped him in a crystal cage before reading the spell to call upon the Halliwell Ancestors. The resulting explosion deactivated the crystal cage, but was not enough to vanquish Barbas. ("Sympathy for the Demon")

Paige orbed crystals around the demon Jinny to trap her in the conservatory until she had time to deal with her. But before she could, Jinny summoned the magic carpet to fly in and at the cage, incinerating the carpet and short circuiting the cage disabling it so she could walk out. ("I Dream of Phoebe")

It could be possible that the more crystals set in the trap the weaker the cage's shielding ability as the only times the crystal cage has been broken has been when there were five, not four, crystals in it, although it could be just a coincidence.

Billie used her new blasting power given by the Golden Belt of Gaea to send the crystals flying that deactivated the crystal cage she was trapped in.

Lastly there is a demonic version of the cage constructed using pink crystals. This version, however, is smaller and also it appears to be weaker as Christy was able to break through it with pyrokinesis.