Go back in time, where you had to sluice for your gem stones (yes, and walk up hill, in the snow, both ways). We have the sluice, the water and the gems and now all we need is you! You can find such wonderful gems as amethyst, calcite, pyrite and rose quartz. Rocks are our livelihood here at the Mark Twain Cave. If it weren't for the rock called Louisiana Limestone we would not have this wonderful cave! (Ok, the Mississippi River played a part in the formation, too). Louisiana Limestone is found only between Hannibal and Louisiana, Missouri; about a 35-mile stretch. Louisiana limestone is soft limestone, so when the water seeped in the cracks and crevices, a process called "solution" occurred and formed the cave as it is today. While the limestone is 325 million years old, the cave itself is only about 10 million years old. It is speculated that Mark Twain Cave and Cameron Cave were once connected as one. Then a glacier came through during the Ice Age and separated the two caves with a valley. That time also brought the glacial clay that is the "floor" of the cave. So, you see, we love rocks!
