Yes. Trays are well suited to individual resale, but the number, size and character of the specimens can vary. It makes sense to inspect each delivery and price individual pieces according to their size, formation and overall appearance rather than assuming every specimen in the tray has equal retail value.

Not necessarily. Some mineral formations are quite fragile, and this range also includes galena, where that dust may be toxic if inhaled or ingested. Delicate or potentially dusty specimens are better kept in a cabinet or handled under staff supervision.

No. Minerals vary considerably in hardness, chemical stability and fragility, so one cleaning method is not suitable for the whole range. For ordinary shop dust, start with a soft brush or air puffer and avoid soaking, scrubbing or using household chemicals unless you know the particular mineral can tolerate it.

They can certainly be interesting for learning about geology, but the whole family should not automatically be treated as children’s products. Some specimens may have sharp or fragile crystal formations, while certain minerals contain elements that call for more careful handling, so adult-supervised educational use is the safer positioning.

Yes, keeping it reasonably dry is important. Pyrite can oxidise in humid conditions and may eventually develop powdery or crumbling areas; conservation guidance identifies relative humidity above about 50% as a particular concern for susceptible specimens.

Separate it from neighbouring stock rather than brushing the loose material around the display. Some minerals can deteriorate through changes in humidity, oxidation or other environmental conditions; pyrite is a well-known example, so affected pieces are best kept dry and handled as little as possible.