Most crystal-care advice is written as though every stone were the same substance. They are not. They differ in hardness, in solubility, in how they react to light, and the differences are measurable. Below is what each common method does physically — and which stones it ruins.
What follows makes no claim about energy. It is about what happens to the material.
Water
Do not soak: selenite, halite, malachite, pyrite, lapis lazuli, turquoise, angelite, calcite.
Selenite is gypsum, and gypsum is soluble. Water does not clean it, it dissolves it — slowly, invisibly at first, then as a chalky dullness where the polish used to be. The same is true of halite, which is rock salt and will simply disappear.
Malachite is a copper carbonate. Prolonged water contact degrades the surface, and the dust from a damaged piece is not something to breathe or leave where a child might. Pyrite is iron sulphide and rusts. Lapis and turquoise are frequently stabilised with wax or resin that water lifts, taking the colour with it.
Quartz and its family — amethyst, rose quartz, citrine, agate, carnelian, jasper — are fine in water. So is obsidian, which is glass.
Sunlight
Will fade: amethyst, rose quartz, citrine, fluorite, celestite, kunzite, smoky quartz.
This is the one that surprises people, because leaving stones on a sunny windowsill is recommended constantly. In amethyst the purple comes from iron in the crystal lattice altered by natural radiation over geological time. Ultraviolet light degrades that colour centre. A good amethyst left in a south-facing window for a summer will come out visibly paler, and it does not come back.
Rose quartz fades the same way. If you want light, moonlight is at least harmless.
Salt
Avoid entirely on: anything soft, anything porous, anything metallic, anything with a polished face you care about.
Dry salt is an abrasive with a Mohs hardness of about 2.5, which means it will scratch every stone softer than that — selenite at 2 above all — and will work into the fissures of harder ones. Salt water attacks metal settings and any adhesive. Burying an item of jewellery in salt is a reliable way to loosen its stones.
Salt is genuinely fine for tumbled quartz. It is a bad default.
Smoke, sound, moonlight, selenite plates
These are the physically harmless ones, which is presumably why they are recommended for everything. Smoke deposits a small amount of residue on a porous surface over years; sound and moonlight do nothing measurable to the material at all.
Laying stones on a selenite plate is safe for the stones. It is worth noting the plate is the soft one in that arrangement — put a quartz point down hard on selenite and you will mark the selenite, not the quartz.
The one that actually matters
Dust. Natural stone in a British house collects a fine film that dulls everything, and no amount of moonlight touches it. A dry, soft brush — a clean make-up brush is ideal — into the crevices of a cluster, once a month, will do more for how your collection looks than every method above combined.
A short table to keep
- Safe in water: quartz family, agate, jasper, obsidian, aventurine.
- Never in water: selenite, halite, malachite, pyrite, turquoise, lapis, calcite.
- Never in direct sun: amethyst, rose quartz, citrine, fluorite, celestite.
- Never in salt: selenite, anything set in metal, anything polished.
- Always safe: a dry brush and a soft cloth.