Rock

Chert

My name is Chert. I am a cryptocrystalline silicate, which means my crystals are so small and transparent that you can not see them without a microscope. I use this to my advantage. I have been strategically lying beside Waller Creek in search of the albino squirrel. Day and night, I have been on the lookout, but have yet to track him down. Luckily, I have a great group of friends waiting for me. Actually, we are hanging out later if you want to join.

Formation

Chert is a sedimentary rock composed mostly of chalcedony. Sedimentary rocks are formed near the Earth's surface through compression.

Identification

• Hardness: 7 Mohs Hardness Scale
• Grain size: Fine
• Special characteristics: Previously used to make tools and weapons

Click to learn about the special role of Chert in Texas history.