Agate is a cryptocrystalline silicon dioxide (SiO2) with a hardness of 7-8.
Method for testing the Mohs hardness of agate
Because the Mohs hardness of agate is more than 7.
When we can scratch the surface of real agate with jade it will not leave marks.
Most of the fake agates are made of other materials, so scratching the surface with jade will leave traces