What types of resources did explorers find in Texas?

Actually, the explorers didn't find any riches in Texas. The indigenous population of the region, back then, told the explorers many stories about riches on other places, which motivated exploration for the next 70 years.

Still, no gold was found in the region nor anything of value to the Europeans, who eventually gave up on searching for riches in the area.

Texas' natural resources today are mainly mineral, gas and oil. Back in the age of exploration, the technology to use such resources didn't exist, but Texas was still rich in other things, especially fertile land near the rivers basins, edible crops and wild plants and specially animals to hunt, such as the buffalo or deer.