Start by asking your kids, “If you lost your favorite possession, what would you do to try and find it? What senses would you use?” Discuss what senses can be helpful to identify an object, then ask, “Do you think you could identify a rock without actually seeing it?”  This is going to be the challenge!  Send kids outside to find a rock about the size of a golf ball.  Sit down together and ask kids to do a sensory exploration of his or her rock.  For example: 

• Look for sharp points and smooth places
• Is your rock cold against your cheek? 
• Is it heavy or light? 
• Smell three parts of your rock. Any surprises? 
• Tap your rock with your fingernail.  What sound does it make? 
• Imagine getting smaller and smaller until you are so tiny that you can explore your rock if it were a small planet.  Where would you plant a garden?  Where would you put a lookout tower? Where would you collect rainwater? Where would you build a house? 

Collect the rocks and ask your child to close their eyes or put a blindfold on them.  Randomly hand them a few rocks (including theirs)  and ask if they can identify their rock using their senses.  My son immediately felt for the parts of the rock where he said he would plant a garden and put a lookout tower and then he correctly identified his rock!  This inspired us to go out and find more rocks and try the activity all over again.