Seventh graders are investigating the growth and development of table salt and Epsom salt as part of their geology unit. Rocks are made of minerals, and minerals grow in distinct crystalline structures. As we are seeing, table salt grows in cubic formations, while Epsom salt grows in needle-like pillars. The lab has been going on for several weeks. Like middle schoolers themselves, the crystals are growing at different rates! (In one image of Epsom salt, the tip of a mechanical pencil is inserted for scale reference.)
The crystallization on and around the beakers has also lent itself to better understanding how chemical sedimentary rocks form. Rocks such as limestone and rock salt form as oceans evaporate and minerals come out of solution. The evaporating water tries to carry the solute with it, but eventually "drops" it.