When it comes to cleansing them, please cleanse them by smudging with sage, or placing them on true Selenite, or Satin-spar selenite. Even better when you do both smudging and Selenite cleansing, especially when they have taken on a lot of energy. I believe every crystal should be cleansed, but almost every crystal must be cleansed often as they absorb a lot of energy throughout the day and night. Selenite, Kyanite, and some say Citrine never need to be cleansed. But I always do for good measure. Smudging for the Selenite, especially since it cleanses all of the other crystals so often.
They recharge with the moons energy, so place them out in the moonlight (on a windowsill is fine) on full moon nights. Remove them from the windowsill or wherever you are keeping them to sit in the moonlight before the sun touches them, or the will lose some of their moon energy they absorbed.
They also can be charged in soft exposure to the sun, but for crystals like Amethyst, Rose Quartz, Smoky Quartz, and Citrine for example the sun can fade the color out, so be cautious.
To determine what crystals should not be in the sun is to observe the transparency of your crystals. Most crystals that are transparent or semi-transparent should not be exposed to sunlight as they are prone to their colors fading or the crystals cracking with the heat and light exposure.
Just like there are a variety of crystals with numerous healing powers and qualities to them, the amount of time crystals can be exposed to sunlight varies too.
Below is a brief list of what crystals should not be in the sun, but make sure to do your own research on what other crystals can or cannot be exposed to light. Some transparent crystals can only be exposed to sunlight for 5 minutes while others will be safe with exposure up to 30 minutes.
Amethyst
Rose Quartz
Smoky Quartz
Celestite
Citrine
Ametrine
Aquamarine
Fluorite
All Quartz
Opal
Apatite
Aventurine
Calcite
And some Jaspers as well
Copper
Copper will naturally patina with age, and with extended wear. Please do not swim or bathe with this handmade jewelry on, it will cause the piece to patina more quickly. If you wish to remove the patina, please use proper cleaning solution and methods.