Crystals
From Steak Wiki
A rock that vibrates. Piezos. You can have your piezo and eat it too (if it's salt).
Computers are a calculating rock.
LEDs are a rock that emits light.
Magic rock.
List
- https://youtu.be/MbPeYd1N1Xg - How to characterize crystal parameters. This video walks through turning a crystal into a strict electrical circuit, so you can adjust the frequency, or calculate what capacitance is needed. This subject matter is also covered in AoE, 3rd edition, section 7.1.6.