January 7 Celebrates Old Rock Day

Mountains in Texas

As Texans, we’re surrounded by history more than a billion years old. It’s in the rocks and minerals and fossils that shape the Lone Star landscape. And it’s in the wealth of natural resources the rocky Texas terrain continues to ooze forth.

January 7 celebrates that history with Old Rock Day. Let’s take a brief look at rocks in Texas.

State sanctioned. Petrified palmwood, a type of fossilized tree, was adopted as the state stone in 1969. It can be found throughout Texas and is thought to date to the Oligocene Epoch (Cenozoic Era) about 30 million years ago. That’s when much of the state was covered in swamps and palm forests. The same year the state stone was chosen, Texas adopted blue topaz as its state gem—along with a faceted gem design known as the Lone Star Cut.

Layered like a cake. Texas rocks are organized by scientists into four major periods based on age. The Precambrian Eon, up to a billion years ago, forms the oldest layer, though earth forces have pushed these rocks to the surface in places like El Paso. Then there’s the Paleozoic Era, characterized by rocks formed when Texas was under the sea 600 million years ago. These rocks include sandstone, shale and limestone. The Mesozoic Era came next—about 240 million years ago—and represents still more time beneath the sea. And then last but not least came the Cenozoic Era, when the seas retreated and land animals and plants like the palms that would one day become the state stone began to take hold.

Sights to see. A rich geological history usually means lots of great sights to take in. And that certainly holds true for Texas, where places like Enchanted Rock State Natural Area and Big Bend National Park have become increasingly popular destinations over the years. You can even find a little mystery—if that’s what you want—in features like the famous rock wall of Rockwall, Texas. No one is sure who built the wall, or even if it was built at all—some believe it to be a natural feature, even though it looks as if it were built by human hands. Or maybe you just want to get outside and do a little rockhounding of your own. Texas is loaded with rocks and gems, and they can be found just about anywhere.

It’s clear geology is important in Texas. It can teach us about the past, and it can help us understand the present as it continues to play a part in the story of the Lone Star State. Happy Old Rock Day.