A beginners guide to identifying and caring for crystals

Before a stone is anything else, it is a mineral: a solid with a definite chemistry and an orderly internal structure. This guide is about that layer — how to tell one crystal from another, how to spot common lookalikes and fakes, and how to clean and store different stones without damaging them. It makes no claims about wellbeing, wealth or outcomes of any kind. It is mineralogy and object care, nothing more. For the wider background on what crystals are and the ethics of the trade, see crystals as mineralogy.

The properties that actually identify a stone

Mineralogists identify specimens by a small set of physical properties. You can use the same ones at home, with no special equipment.

• Hardness is measured on the Mohs scale from 1 (talc) to 10 (diamond). It is relative — it tells you what scratches what. Useful reference points: a fingernail is about 2.5, a copper coin about 3.5, ordinary window glass and a steel knife blade about 5.5, and quartz is 7. So quartz will scratch glass; calcite (hardness 3) will not, and is itself scratched by a coin.
• Cleavage and fracture describe how a mineral breaks. Cleavage is breakage along flat planes fixed by the crystal structure: mica peels into sheets, calcite splits into rhombs, fluorite into octahedra. Fracture is breakage that is not along a plane — quartz breaks with the curved, shell-like “conchoidal” fracture also seen in glass.
• Crystal habit is the characteristic shape a mineral tends to grow in — quartz’s six-sided prisms with pointed terminations, pyrite’s cubes, garnet’s rounded many-faced crystals.
• Lustre, colour and streak. Lustre is how the surface reflects light (glassy, metallic, waxy, pearly). Colour alone is unreliable because trace impurities change it. Streak — the colour of the powder left when a stone is rubbed on unglazed porcelain — is often more constant: hematite, whatever its outward colour, leaves a red-brown streak.
• Specific gravity is relative density — how heavy a stone feels for its size. With handling you learn that, say, a piece of barite feels notably heavier than a same-sized piece of quartz.

Common lookalikes

A handful of confusions come up constantly, and the identifying tests above resolve most of them.

• Pyrite vs. gold. “Fool’s gold” is brassy and forms cubes; it is brittle and gives a greenish-black streak. Gold is far denser, malleable rather than brittle, and gives a golden streak.
• Quartz vs. calcite. Both are common and clear-to-white. Quartz is hardness 7 and will scratch glass; calcite is hardness 3, breaks into rhombs, and fizzes with a drop of weak acid (vinegar).
• Clear quartz vs. glass. Natural quartz often shows internal features and slight cloudiness and feels cool; moulded glass may contain rounded gas bubbles and a mould seam. Both have conchoidal fracture, so use inclusions and shape.
• Nephrite/jade vs. serpentine or dyed stone. Softer green stones and dyed material are frequently sold as jade; hardness and professional testing separate them.

Treated, enhanced and fake material

Much of what is sold has been altered, and honest sellers disclose it. Being able to recognise the signs protects you as a buyer.

• Dyeing. Porous stones like howlite and magnesite are routinely dyed blue and sold as “turquoise.” Dye often concentrates in cracks and can rub off onto a cotton bud dipped in a little acetone.
• Heat treatment and irradiation. Many amethysts become “citrine” through heating; much deep-blue and some smoky material is irradiated. These are stable but should be disclosed.
• Reconstituted and imitation. “Goldstone” is a manufactured glass with copper flecks, not a mineral. “Cherry quartz,” “opalite” and many vivid, perfectly even stones are glass or resin. Perfectly uniform colour, gas bubbles, moulded shapes and prices that seem too good are all warning signs.
• Glued or dyed “geodes” and assembled pieces. Some display items are dyed and cemented. A hand lens revealing a seam or adhesive is the giveaway.

None of this makes treated or manufactured material worthless — it just needs to be sold as what it is. The problem is misdescription, not the object.

Cleaning by mineral type

“Cleaning” here means physical care only — removing dust and grime without harming the specimen. Different minerals need different handling, and the wrong method ruins stones.

• Hard, non-porous stones (quartz family, agate, most jaspers) tolerate lukewarm water with a soft brush and mild soap. Rinse and dry well.
• Water-sensitive and soft stones should be kept away from water. Selenite (a form of gypsum, hardness ~2) will pit and dissolve with prolonged wetting; halite (rock salt) dissolves readily. Dust these dry with a soft brush or cloth only.
• Porous and dyed stones (turquoise, malachite, dyed material) should avoid soaking, which can leach colour or, with malachite, is inadvisable because its dust is not something to inhale. Wipe gently and keep dry.
• Reactive stones — anything containing carbonate, like calcite and malachite — must never meet acids, including vinegar and even acidic skin products, which etch the surface.
• Avoid harsh methods such as ultrasonic cleaners and strong chemicals unless you know the specimen tolerates them; they crack fracture-filled or included stones.

Light-fastness and storage

Some minerals fade in light, and this is genuine mineralogy, not superstition. Amethyst, citrine, rose quartz, fluorite, celestite and kunzite can lose colour with prolonged exposure to strong sunlight, so display coloured quartz and these others out of direct sun. Store softer stones separately from harder ones so a piece of quartz (7) does not scratch a piece of fluorite (4) or calcite (3); individual boxes, pouches or compartment trays work well. Keep water-soluble specimens somewhere dry and stable, as high humidity alone can degrade halite and, over time, some others. Label specimens as you acquire them — locality and any known treatment — so your collection stays honest and useful.

The honest bottom line

Identifying and caring for crystals is a satisfying, evidence-based hobby in its own right. Hardness, cleavage, habit, streak and density will tell you what a stone actually is; a hand lens and a few simple tests will flag most fakes and treatments; and matching your cleaning and storage to the mineral keeps specimens intact for decades. That is the whole of it. This guide makes no claim that any stone affects the body, mood, wealth or events — it is about knowing your minerals and looking after them well.