Quartz crystals are amazing
They are usually 3-5 times longer than their hexagonal cross-section.
They are usually single terminated which means they have one pointy end.
The other end is broken where the crystal was broken from its host. This end can be cut to a tip to make it a double terminated crystal.
A Quartz crystal has 3 faces it can be cut across.
All 3 faces have different properties.
They are not often perfect but that is not important for their use here.
There are two crystals that are Piezo Electric, they are Quarts and Pink Salt.
We use a large ½ diameter terminated Quartz Crystal at the tip of the cone. Quartz will take on the properties of other crystals near by, this effect is amplified when the crystal is under pressure. Because When the resin sets it shrinks which compresses this crystal putting it into a Piezoelectric state.