Crystaline formation. My guess is, as you get closer, you see broken shards of crystal on the ground. Similar to the statue down in the desert in the south east part of map. There is a tall statue that you can see wobble from a distance, but as you get closer..*poof* it disappears, but you then walk to where it was, and you see it laying on the ground after having fallen. Just a guess though. :-)
If ur asking what the dark lines extending beyond the crystal are, It looks like because of the shining lightsource slightly below and behind the crystal, ur video card tried to draw a shadow of the crystal and it projected the shadow because of the position of the lightsource into the air above it.
