Not all diamonds have the same hardness.
Needham used to be covered by a glacier.
The large rock on the playground is actually made up of igneous, sedimentary and metamorphic rock. The blue-ish rock is igneous.
Lichen grows on rocks.
On the small rock you can see lines that are all going in one direction. These were made by glaciers scraping the rock as the glaciers moved.
Mr. Dodson is a geologist. He tests rocks that are underground to figure out if they are hard enough to build on. They do this by drilling holes into the rocks. The biggest drill they use is 6 feet wide. Sometimes they fill the hole with concrete.
Water can move large rocks.
Water can be strong enough to break rocks over a long period of time.
Granite is a very hard rock and is used for many things - even making countertops.
Windows used to be made from a mineral called micah. (Not our Micah. )
Micah was used to make windows because it is very thin and you can see through it.
Click here to see pictures from Mr. Dodson's visit.