How imitation stone is made

“Fake” is too blunt a word for what’s happening in the low end of the stone trade, because at least five distinct things get called it and they’re not equivalent.

A dyed stone is a real mineral with added colour. A reconstituted piece is real mineral powder in a binder. A glass piece contains no mineral at all. A polymer-impregnated piece is a genuine specimen whose structure has been rebuilt. These differ in what they’re made of, in how they’re produced, in what they do over time, and in what evidence they leave for someone examining them.

Knowing the process is the only route to knowing what to look for.

Dyeing

The most common treatment by a wide margin, and the easiest to understand.

Porous or fractured stone is soaked in dye — sometimes under heat or pressure to drive it further in. Pale serpentine becomes convincing green; grey quartzite becomes a saturated colour; low-grade jadeite becomes the intense emerald tone that commands a premium.

What it leaves behind. Dye does not distribute evenly. It travels preferentially into fractures, grain boundaries and porous zones, and it concentrates there. Under magnification — even a cheap loupe — dyed stone typically shows colour pooling along fine cracks and in a web-like pattern between grains, rather than the colour sitting in the body of the material. Natural colouration follows the mineral’s own structure, which usually looks different: banded, mottled, or associated with visible inclusions.

Other traces: dye colour is often too even in the bulk and too intense at the edges. Some dyes transfer slightly to a swab, though this is unreliable and many modern dyes don’t. Some fade with prolonged UV exposure over years.

Waxing

Old, widespread, and generally accepted.

A thin surface coating of wax fills microscopic pits, improves polish and deepens apparent colour. In the jadeite classification it’s compatible with Type A — natural, untreated — because it’s a surface finish rather than a structural intervention.

What it leaves behind. Very little that matters. A slightly greasy feel when new. Wax can be softened by heat, which is one mechanism by which a stone’s appearance changes after contact with very hot water.

Polymer impregnation

The serious one, and the reason the A/B/C classification exists.

Low-grade jadeite that is structurally sound but visually poor — stained, cloudy — is treated with strong acid to bleach out the staining. That process removes material and leaves the stone porous and weakened. It’s then impregnated with a clear polymer resin under pressure, which fills the voids, restores mechanical integrity, and dramatically improves translucency.

The result is genuine jadeite by composition. It is also substantially a composite object, and it’s classified Type B.

What it leaves behind. Polymer-filled stone often fluoresces under UV in a way untreated jadeite does not — a chalky glow, sometimes patchy. Under magnification the surface can show a fine network of etched channels where acid attacked grain boundaries. Infrared spectroscopy detects the resin straightforwardly, which is how it’s actually confirmed.

What it does over time. Polymer ages. Type B material can yellow, cloud, or develop surface crazing over years. This is a real difference in durability, not merely a disclosure issue.

Reconstituted stone

Crushed genuine mineral, sometimes waste from cutting, bound with resin and moulded or pressed into shape, often with dye added.

Common in inexpensive turquoise and increasingly present anywhere a material is expensive and a powder is cheap. Sometimes sold with honest labelling (“reconstituted”), sometimes not.

What it leaves behind. Under magnification, a suspiciously uniform texture with visible grain boundaries in a matrix — it looks like what it is, a particulate suspended in something. Density is usually low for the claimed material because resin is much lighter than stone. It’s often warmer to the touch than solid stone for the same reason.

Glass

Not an imitation of a treatment; a different substance entirely.

Moulded glass, coloured and sometimes swirled to suggest natural variation, is cheap to produce in quantity and takes a good polish.

What it leaves behind. The tells are reasonably accessible:

Bubbles. Spherical gas bubbles trapped in the body of the material are diagnostic of glass. No natural stone contains them. A loupe finds them.

Swirl patterns that flow rather than band — glass moves as a liquid and the internal patterning follows fluid dynamics, not crystal growth.

Mould seams, usually polished away but sometimes detectable at edges.

Conchoidal fracture — chips are curved and shell-like, with sharp edges.

Warmth. Glass has lower thermal conductivity than most stone, so it warms faster in the hand. This is a genuine physical difference and a weak test, since the difference from some stones is small.

Obsidian is worth noting here, because obsidian is natural volcanic glass — it also fractures conchoidally and can contain bubbles, and it’s a legitimate material for these tools. So “it looks like glass” doesn’t settle much on a black stone; it settles a good deal on a green one.

Resin and plastic

At the very bottom of the market, moulded resin with pigment. Distinguished from glass by being much lighter, softer, and warmer; scratches easily; sometimes has a faint smell when warmed by friction.

What you can tell

WHAT YOU CAN TELL — with a 10× loupe and daylight

  · Spherical bubbles inside the material
                        → glass or resin. Reliable.

  · Colour concentrated along fine cracks, web-like
                        → dyed. Strong indicator.

  · Flowing swirls rather than bands or mottling
                        → glass

  · Particles visible in a uniform matrix
                        → reconstituted

  · Much lighter than expected for the size
                        → resin, glass, or a lighter species
                          than claimed

  · Warms very quickly in the hand
                        → weak indicator only; low thermal
                          conductivity. Not diagnostic.

  · Chalky fluorescence under UV
                        → possible polymer impregnation;
                          suggestive, not conclusive

  · Whether an untreated-looking stone is Type A
                        → NOT DETERMINABLE at home.
                          Needs spectroscopy.

Why this is so common

Not primarily because the trade is dishonest, though some of it is. Three structural reasons:

The treatments are legal and often disclosed further up the chain, then lost by the time a listing is written by a reseller who may not know either.

Trade names do a lot of the work. A stone sold as “new jade” is being described accurately by trade convention even though the buyer reads it as jade.

The economics are decisive. A gua sha tool is a small, thin, flat piece of stone sold at a price point where genuine untreated material of good colour is simply not available. Something has to give, and the market has arranged for it to be the material rather than the price.

The limit

Every indicator above is suggestive rather than conclusive, except the bubbles. A loupe and good light will tell you when something is clearly glass or clearly dyed. Nothing available at home confirms that a stone is untreated natural material of a particular species — that requires a gemmologist, and the tests you can run yourself should be understood as ways of ruling things out.