My oldest son was learning about dinosaurs in his class and it gave me motivation to do these Do-It-Yourself (DIY) Dinosaur Eggs (or rocks if you don't want to shape them into eggs.)

We had all the ingredients, but I would suspect that some people may not have sand readily available to them. It only takes 1 cup of sand to make the five eggs you see in the photo mixed in with the other ingredients.

The eggs are about 4 to 5-inches long and about 3-inches in diameter and we used an air dry method with plastic dinosaurs (and animals.)

We just did this for fun, but I would expect that these "eggs" could be made in advance of a dinosaur themed party or as part of a dinosaur dig with a group of children.

Overall, it took my kids and I about 30-minutes to mix and mold the eggs, and we waited three days for the eggs to dry. We broke them up again the day after they dried.

From the photo, you can see that the inside doesn't dry all the way through, but the outside is hard as a rock.

Step 1: Materials

Materials used to create these dinosaur eggs are hopefully things you have around the house, or nearby (like for the sand, acquired legally of course.)

1-cup all purpose flour
1-cup coffee grounds (the ones shown are used because I can't waste coffee)
1-cup sand
3/4-cup salt
1/2-cup water (or less, see Step 3)
four to five small plastic animals or dinosaurs

You will also need a large bowl and a tray or plate to set the eggs out to dry.

Step 2: Mix

Having fun with my kids was the sole purpose of doing this, so naturally, they had to mix the ingredients together.

Add the flour, coffee grounds, sand and salt together thoroughly.

Step 3: Add Water & Mix

The less water used, the faster the rocks (or dino eggs) will dry.

There was a little moisture in the coffee grounds, so we only added 1/2-cup of water to the mix in Step 2.

The kids mixed the components of the dinosaur eggs after the water was added, and we knew it was ready when we were able to squish the mix in our hand and it stayed together. More water would do the same thing, but again, the dinosaur eggs wouldn't dry as fast as I state in this Instructable.

Step 4: Mold the Egg Around Your Dino

Taking some of your sand mix, place a plastic dinosaur on top of the mix in your hand.

Add the sand mix on top of the dinosaur, and begin packing around the sides.

Continue adding the sand, flour, salt and coffee grounds mixture and form into an egg to completely cover the dinosaur.

Form the egg shape (or shape into "rocks" if that's what you choose to do) back and forth in your hands until satisfied with the shape.

Step 5: Let Dry

My kids had a hard time waiting the three days it took for these Dinosaur Egg rocks to dry.

We had about 70-degree (daytime) weather while we made these, so I left them outside to dry out.

If you added more water than what I suggested in Step 3, the eggs will take longer than 3-days to dry out.

My kids and I checked on them every day, and after day two, we turned them over on the tray they were drying on to dry the bottom out.
You can see from the photos that if I were more proactive, the eggs probably could have dried in a more egg-like shape, rather than having a flat side from sitting on the tray.

Step 6: Break Open

One of the strange things about children is that even though we made these rocks four days earlier, AND my kids KNEW what was in them, they still wanted to break them open and get what was on the inside right away.

At least they got dirty and had fun.

My oldest son took his hammer, and in a plastic bowl for easy clean-up, each one of my children got a chance to crack open their dinosaur eggs and get their plastic little friend out.

I could see these eggs being part of a dinosaur themed party, buried in a sandbox and picked open with chisels or other actual-dinosaur digging tools (for kids of course).

The outside of the egg is pretty hard, but once the outside is cracked open, the inside was still moist and the plastic friend can be removed easily.

Have fun friends and stay curious.