I made the object editable and then selecting all side applied a matrix extrude
step 3 of 4
At this point I adjusted all of the different setting for a matrix extrude, changing steps, angels etc until I got the spike shape I was looking for.
step 4 of 4
I used a simple glass texture for the crystal and then to colour in the glass I used the lights, two lights, one with a blue tint and one with a purple tint both with reduced intensities until I got the effect I liked. Thats all folks :-)