It looks like you have a nice piece with quartz veining! Quartz is a hard mineral (7 on mohs hardness scale), so, naturally the other minerals weather off before the quartz. What you have left is quartz toughing out the elements. Got any more pictures? It looks like that would be dry mud the way the quartz deposited like that.
Calcite, the most abundant crystaline mineral found in N. Texas.
It is not quartz.
Yours seems to be part of a septarian nodule.
BTW: Place it under a black light.
The closer the light source the more it may "Glow".
Some glow green some orange some yellow.........
Others will not glow at all.
The nodules from the Eagleford shale do glow the ones from the Woodbine deposits do not.
Thank You Rific and bone2stone, I will try to add some more Photos later. It is just an odd shaped rock, kind of looks like a Turtle. When busted open I was amazed at the Crystal looking things inside.
To me it also looks like a nodule, but with quartz-veins rather then calcite. If it is calcite, it will bubble and fizzle if you put a little vinegar on it!