Crystal elixirs, also known as Gem Water, have had a recent resurgence in popularity. The idea is to transfer the healing properties of the crystal into the water so it can be drank as an elixir. This idea has been used for thousands of years, but it needs to be properly prepared so as to avoid potential health problems.
There are two methods traditionally used to create crystal elixirs, the direct method and the indirect method. The direct method involves placing the crystal directly into the water, leaving it for a period of time, then removing and drinking the water. The indirect method does not allow the crystal to come into direct contact with the water that is to be drunk. Considering that most people will not know the origin of their crystals, what chemicals have been used to clean them and even what the crystal is actually made of, then I would never recommend using the direct method of creating crystal water.
Some crystals dissolve in water, such as Halite, or start to change, such as Angelite which will start to turn back into gypsum. Some will start to rust, such as iron based minerals like Hematite. Some have dangerous heavy metal content which you don't want to put into your body, such as Galena. Some crystals will have been cleaned with harsh chemicals in order to make them look more attractive for market, including many Quartz crystals which are often bathed in acid to remove iron staining. For all these reasons and many more, I would not use the direct method to make crystal elixirs.
There are various indirect methods that can be used to create gem water, the easiest is to place another glass or jar with the crystal in, inside a bowl of water, so that the crystal does not come into direct contact with the water. This way the energy of the crystal will still flow out, but you do not risk ingesting anything dangerous. Leave this in the sun or moonlight (depending on whether sunlight will make your crystal fade) for 12 hours, then remove the crystal, and your elixir is ready.