Ornate Uromastyx

What type of substrate is that? Great uros

That is a "decomposed granite". It's supposedly a great soil for burrowing reptiles like uros. You can also use a combination of about 50% soil 25% sand and 25% vermiculite to make a good burrowable soil. You need a minimum of about 8" for them to get good use out of it and you have to experiment with watering to figure out how to keep it at just the right consistency to hold a burrow. Hope I helped a little.