Amethyst

Amethyst is an earth pony who has been infected by the parasitic crystal (her name used to be Indigo, before she decided to change it). She can keep the crystal (sort of) at bay, but this results in the crystal being very infectious to things around her, and she sometimes leaves trails of crystal when she walks. She was infected at an extremely young age, thus even though she has developed a way to slow down the crystal, it had already advanced quite a long way. She often covers up her crystals with a cape.
Her coat is white and her mane and tail are a deep purple colour. Her eyes are jet black, and the colour of the crystal is violet.
She keeps to herself because she doesn't want anypony judging her, and she doesn't want to infect other ponies (or other creatures)

Will update design later.

More info on the Parasitic Crystal here: <da:thumb id="467137500">
Parasitic Crystal (c)