Alpha blending and Lightmapping

In an age I'm working on I've been trying to make a quarry in which there is more than one type of rock blending into others. In order to do this I've duplicated part of the mesh and textured them differently than the initial mesh. Then I used Alpha paint to blend the textures. I then lightmapped the whole quarry. After entering URU, the blending looks fine. However the rock that I duplicated and blended do not show their texture, only the lightmapping.
Here's how it looks in blender:

and here's how it looks in URU:


Notice the brown rock has detail, but the white rock texture is only visible around the edges. Does anyone know what might be causing this?
Here's how it looks in blender:

and here's how it looks in URU:


Notice the brown rock has detail, but the white rock texture is only visible around the edges. Does anyone know what might be causing this?