There are several methods that are used for cleaning/cleansing crystals and what is right for one person isn't for the next. If you are new to cleaning crystals I would reccomend that you try a few different ways until you find what is best for you.
One thing you will see mentioned regulary is that 'anything ending in 'ite' does not belong in water'. Much of this depends on the hardness of the crystal but it's not a hard and fast rule. Some of the 'ite' crystals such as Selenite, which is a member of the Gypsum family, has a hardness of 2 so it will be water soluble. Labradorite has a hardness of 6 - 6.5 so it would take an awful long time or damage to be caused.
If in doubt at all about washing your crystals in water, don't, there are other methods that you can use.
Here is a list of some of the more popular methods, there are more but these are my favourites
Running water in a stream or river is a perfect way to cleanse a crystal. Simply hold the crystal under the water for a minute or so. If you live near the sea saltwater also works well, simply submerge the crystal for a few minutes. If you like the idea of using salt water you can make up a sea salt or Himalayan salt solution at home
You can burn sage, palo santo or cedarwood and pass your crystal through the smoke which will cleanse it
Selenite is very popular for both cleansing and charging. Plave your crystal onto a selenite plate or place it into a bowl of selenite powder. You should leave it around 6 hours to be fully cleansed
This is one thing I have never tried but I have heard good things about it. Using sound that vibrates at a higher frequency than your crystal is also an option to cleanse it. You can chime a singing bowl, or even ring a bell near to the rystal you want to clean
Many people bury their crystals in the earth or in sand. it can be seen as a sort of a rebirth for the crystal to be put back into the embrace of the earth the environment from which it was originally taken