Crystals are generally inert an perfectly safe, however, there are probably two aspects regarding the owning and safety of crystals which you should be aware of:
Children
The first relates to them as a potential danger to children; Because they are often so very beautiful they will inevitably, if the opportunity presents itself, go straight to the mouth of any young child. The most obvious hazard in this case is one of choking so you should be very careful to keep all of your crystals well out of the reach of small children
Toxicicty
Although many of the crystals used in healing are based on some form of Quartz which is completely inert (quartz, citrine, amethyst etc.), others are not (see our Crystal Database for more detailed information if you are interested). The others include minerals such as Malachite which is a Copper ore - a very beautiful one at that. While in normal crystal healing use there is probably no hazard at all from these minerals and even if a child happen to swallow one, it would probably pass through their system without any side effects. Nevertheless, you should be aware that there are crystals out there which under the right circumstances could present a harzard so do your research well - NOTE: We don't stock any crystal which we know to be toxic.
Minerals which contain Lead and Mercury should be handled with care - examples of these are Galena (a beautiful lead based mineral, bright metalic silver coloured crystal which is readily available) and Cinnabar (a dark redish brown ore of Mercury). The latter ore is reputed to have healing properties and is often made into jewellery (we've even trinket boxes made from it). However, any ore of mercury should be handled very carefully indeed and not at all by children.