A Recipe for Rocks

What is the difference between a mineral, a crystal, a rock and a gem?

An element or a compound that occurs naturally, but is abiotic (non living).

“The ingredients of rocks”

A solid made up of molecules arranged in a very specific pattern.

“Chunks of minerals in rocks”

A hard and compact mixture of minerals.

“A smallish chunk of earth.”

1.PLEASE WORK CAREFULLY and try not to spill the Epsom salt.

2.Put on a pair of goggles find a Petri dish and a post it note.

3.Write your names, class period and “Fast Cooling” or “Slow Cooling” on the post it and place it on the bottom of the Petri dish.

4.Take a pipette (eye dropper) and add just enough of the Epsom salt solution to cover the bottom of the Petri dish.

5.Take a small pinch of the Epsom salt crystals and sprinkle them around your Petri dish to “seed” your crystals.

6. If the crystals are fast cooling crystals carefully place them in the refrigerator.

7. If the crystals are slow cooling crystals carefully place them on the counter by the window.

8.Be sure to have one fast cooling and one slow cooling crystal dish per group.

2 5 3 4 1Granite Rhyolite Obsidian Gabbro Basalt

Continental Crust

(Mountains)

Continental Crust

(Around Volcanoes)

Rock cools too quickly

to form crystals (Around

Volcanoes)

Oceanic Crust

Oceanic Crust

Used for countertops

Used for spear heads and scalpels

Makes up sea stacks

and the Columbia

River George

1.There is a good chance that some of your Epsom salt solution is still liquid so handle the Petri dishes carefully.

2.Find your two Petri dishes and compare the size of the crystals.

3.Which has bigger crystals fast cooling or slow cooling?

4.Take a look at the rocks. Which have the bigger crystals. Make the connection.

5.Sketch your crystals (or a different group’s crystals if your crystals didn’t work out) on the table on your lab.

6.When it is time to clean up carefully take off the post it note and then place the Petri dish with the crystals in the sink of the demonstration table up front.

2 5 3 4 1Granite Rhyolite Obsidian Gabbro Basalt

Intrusive Extrusive Extrusive Intrusive Extrusive

Continental Crust

(Mountains)

Continental Crust

(Around Volcanoes)

Rock cools too quickly

to form crystals (Around

Volcanoes)

Oceanic Crust

Oceanic Crust

Used for countertops

Used for spear heads and scalpels

Makes up sea stacks

and the Columbia

River Gorge

Discovered in 2000 by a mining company in Chihauhua , Mexico

300 meters (980 ft) below ground (under the Cave of Swords)

Gypsum (CaSO4) Crystals58 C (136 F)90-99% humidity500,000 years to formLargest crystal:

12 m (39 ft) long 4 m (13 ft) in diameter

55 tons

Exposure time for humans is about 10

minutes without protection.