There are many ways to cleanse and charge your crystals.
One of them is cleansing it fully with Hematite and then charging it with clear Crystal Quartz.
Hematite has a lot of grounding energy and release negative energy. While the Quartz is a Healer and Amplifier.
Just place the crystal you wanna cleanse and charge in a bowl with Hematite
for some Hours and then in the Bowl with the Crystal Quartz, the same.