A basic field microscope (pocket microscope) is relatively inexpensive - about $5 to $15 depending on what you buy or where you get it. They work great too! Letting your kids see the fine details of the minerals that make up their fossils. This "lab work" can be done as a part of a fossil dig/excavation it can be done as a stand alone activity. Photos below were taken with an iPhone clamped on to a field microscope.
What you'll need
  • Fossils - either the ones collected from your dig/excavation or specimens purchased specifically for this activity.
  • A field microscope. (See tools buying guide for recommendations).
What to do
Take each of  your fossils, or a select few, and press the end of your field microscope against the fossil. If you have the kind with a light, turn in the light, it will make it easier to see. Look for things like 
  • Does a smooth surface look smooth under the microscope?
  • Look at the inside of a cracked fossil, how does the inside compare to the outside?
  • Look at a fossil with patterns, such as a snail or ammonite. How do those patterns look up close?  
Picture
Mosasourus tooth - 65 million years old. Full fossil (above) with surface grooves under a microscope (below)
Picture
Crow shark tooth - 70 million years old. Full fossil (above), serrated edges under a microscope (below)
Picture
Cracked spinosaurus tooth - 100 million years old. Fossil fragment (above) with interior mineral formations (below)
Picture
Fossilized amber - 15 million years old. Amber fragment (above), insect under a microscope (below)