If you microwave a rock with iron it will usually heat up and may sometimes spark.
But if you microwave a rock without iron or just a regular rock it may not even heat up or do anything.
What happens when you microwave a rock depends on the type of rock you're microwaving.
Rocks containing minerals with semiconducting or conducting properties will heat up.
So, iron or nickel sulfides, iron oxides, graphitic minerals, etc. will heat up.
If you pick the wrong rock and apply too much power, the pressure increase may cause an explosion that will damage the inside of your microwave cavity.
Some rocks, like those made of silica, are microwave transparent.
And so the microwaves will pass through and nothing will happen.
For other materials that are highly magnetic, the material is too conductive and microwaves will be reflected.
The fact that microwaves can be used to warm up food is well known.
It is less obvious, however, that microwaves can also be used to heat up rock.
A rock is an aggregate of one or more minerals, or a body of undifferentiated mineral matter.
Common rocks include granite, basalt, limestone, and sandstone.
Extrusive, or volcanic, igneous rocks are formed when molten hot material cools and solidifies.
There are three main types of rocks: sedimentary, igneous, and metamorphic.
Each of these rocks are formed by physical changes such as melting, cooling, eroding, compacting, or deforming that are part of the rock cycle.