Crystals and Gemstones bring so much beauty into a home, yet like everything else they do get dusty or dirty. Physically cleaning your crystal beauties can be a little tricky. With so many variations of chemical constituents it is best to use caution as some crystals can be badly affected by water especially salt water. Selenite for example will dissolve if left in water. Others like Angelite/Anhydrite will start to morph into other crystals, in this case Gypsum. Rain or ocean baths are a no no for these crystals.
Some crystals contain toxic compounds which are bio-active & released by water, Malachite & Calcanthite are both bio-active copper minerals. This means they are potentially dangerous & need to be handled with care, best to not wet them. Minerals like Opal & Orpiment are hydrous, they need to retain a certain amount of water to maintain mineral structure. Orpiment contains Arsenic which is released in dust/powder form when the mineral dries out (Keep in a zip lock bag or airtight container to manage risk of exposure). 
*There are many many other crystals which have special needs the above is just a short example. 
To play it safe we recommend the following:

Crystal specimens or other natural minerals 
Physically cleaning: To remove dust from a crystal we often use a camera lens blower on delicate unwashable crystals. For washable crystals simply rinse in room temperature water & allow to dry naturally. Do Not use detergents or chemicals to clean your crystals. To avoid damage look into your crystals specific handling requirements, many can not be exposed to water.

Energetic cleaning: Smudging with sage or Bay leaves. Vibrational resonance such as singing bowls, mantra chanting & frequency music. The full moon (more of a charging than a cleansing energy) or simply placing them on the Earth to ground/reset. Other crystals such as Carnelian, Selenite, Kyanite & Citrine will cleanse the energy of themselves & surrounding crystals. 

Crystal & Gemstone Jewellery
Crystal jewellery must be handled with care & never exposed to water for prolonged periods of time, especially salt water, DO NOT wear crystal jewellery in the shower or swim with it & do not expose jewellery to chemicals. Check out the Jewellery care & cleaning link below

How To's