Martin Clevenger, age 10, Of Visalia, Calif., for his question:

How are geodes formed?

When you find a pebble that feels a lot lighter than its neighbors, you might. be lucky. It may be a hollow geode lined with dazzling walls of semi precious

Crystals. The process started ages ago in a bed of rock. Here and there the bedrock was riddled with holes and cavities. Through the ages, water, bearing dissolved minerals, seeped through its pores and pockets.

Some of the minerals were deposited and left to crystalize on the walls of the empty pockets. In time they formed layers of colored quartz crystals or perhaps bands of agate. You see these beautiful linings when you break open the geode  and where yoy find one geode you are likely to find others, which have formed in the same bedrock.