How to Cleanse Crystals
8 Methods, and the 15 Stones Water Ruins

Selenite is gypsum, and gypsum is soluble in water. A rinse leaves the surface chalky, a soak destroys the fibrous structure, and a wand left in a glass will eventually disintegrate. This is the clearest case on the list and the one most often ignored, because selenite is sold as a cleansing tool itself.

Anhydrite is the dehydrated form of the same calcium sulfate. Add water and it slowly reverts toward gypsum, which is a chemical change rather than a stain. The surface goes dull first and does not come back.

Strontium sulfate, soft and perfectly cleaved. The delicate blue crystal tips that make celestite worth owning are the first thing water and handling take off. Dry methods only.

Copper carbonate. It reacts with anything acidic, including tap water in many regions, and the wet slurry produced by grinding or prolonged soaking carries soluble copper. Treat malachite as a display and handling stone, never as one that goes in water or in a drinking glass.

The same copper carbonate family as malachite, and even less stable: azurite alters toward malachite over time in humid conditions, which is why old specimens turn green at the edges. Keep it dry and out of direct light.

Iron sulfide. Moisture plus oxygen starts an oxidation reaction that mineral collectors call pyrite decay: the specimen sweats, gives off a sulfurous smell, produces sulfuric acid and crumbles from the inside. It is not reversible. Store pyrite dry and away from humid rooms.

Fossil resin rather than a mineral, at 2 to 2.5 on the Mohs scale. Salt scratches it, alcohol and solvents cloud it, heat softens it, and prolonged water dulls the polish. Wipe with a soft dry cloth and nothing else.

A lithium mica, which means it is built in sheets. Water works into the layers and lifts them, and a piece that arrives whole comes apart along its own bedding. Rough lepidolite is more vulnerable than polished.

Hydrated copper silicate, often soft enough to mark with a fingernail and frequently stabilised with resin before sale. Water attacks the stone and the stabiliser at once, and the copper content raises the same concern as malachite.

Porous and, in the overwhelming majority of commercial pieces, dyed. Blue howlite sold as turquoise gives up its dye in water within minutes, which is also the cheapest way to identify it. Undyed white howlite survives a quick rinse but stains readily.

A hydrous phosphate, porous by nature. It absorbs water, oils, perfume and sweat, and the classic sky blue shifts toward green as it does. Most turquoise on the market is stabilised with resin precisely because untreated material is this fragile.

Calcium carbonate, so it dissolves in anything acidic and etches in ordinary tap water depending on where you live. The same chemistry as limestone, and it weathers the same way.

Not water-soluble, but calcium fluoride cleaves perfectly in four directions and chips from a knock or a temperature change. A cold rinse on a warm stone is enough. Colour also fades under sustained sunlight.

Blue pectolite, soft enough to scratch against most household surfaces and known to lose colour with prolonged sun exposure. Brief contact with water is survivable, soaking is not worth the risk on a stone this expensive.

The unusual case: kyanite has two hardnesses on the same crystal, around 4.5 along the blade and up to 7 across it. It splits along its length with almost no force. Water does no chemical damage, handling does the damage, and a soak means handling.