So, where did you find it? Does light shine through it when you back light it. Is it smooth or rough. To me it looks like weathered quartz. The rock may have some staining from trace elements. If it was found near water, that would explain the weathering. As a matter of the back lighting, that will tell you if the rock is translucent. I suspect it will light up if you hold it in front of a light source. You may be able to see inclusions, cracks and such which you cannot see without the light.