Jade bangle changes colour with wear.

I bought a lavender jade bangle and it was quite lavender when new.
I wear it a lot...on an everyday basis.
It is no longer lavender....within a short while of wearing it from new, it started to change colour.
Now it is quite green with just a couple of tiny lavenderish patches. Sometimes it appears more clear than other times too.
I have an amethyst crystal pendant too that gets clearer and a little purpler when I wear it. Does anyone know about this curious property? Do other crystals change too?

Hi Feather I did hear once that crystals which fade in colour are 'drained' I'm not sure if this is true or not, as for the other becoming brighter are some heat/energy sensitive I wonder?

It would be cool if that were the case!