Spotting Fake Gemstones at Home: Simple Checks and Their Limits

Fake stones are a real worry for buyers in Pakistan, and with good reason. Markets carry glass sold as Zamurd, plastic sold as Kahruba and dyed powder sold as Feroza. You can catch a lot of this at home. You cannot catch everything, and it helps to know where home testing stops.

Tools worth having

• A 10x jeweller's loupe, which costs little and shows far more than the naked eye.
• A small torch or phone light.
• Cotton buds and nail polish remover containing acetone.
• A glass of water and some table salt.

Always test unset stones where possible, and never do anything that scratches, heats or soaks a stone you have not yet paid for.

Glass

Glass is the oldest imitation and still the most common. It can be made in any colour, including convincing blues and greens.

• Bubbles: under a loupe, round gas bubbles are a strong sign of glass. Natural gems have crystals, needles and feathery fractures instead.
• Swirls: curved flow lines inside a stone point to glass.
• Worn edges: glass is soft, around 5.5 in hardness. Facet edges on a glass stone that has been carried around look rounded and chipped, with shell-shaped nicks.
• Touch: crystalline gems tend to feel cool and warm slowly. Glass warms faster. This is a hint, not proof.

Do not try a scratch test. It damages both stones and proves little.

Dyed agate

Agate takes dye readily, and much black, green and blue agate is coloured on purpose. That is a traditional treatment, not a fake, but you deserve to know. Signs of dye:

• Colour concentrated in cracks, pits and along band edges.
• Colours too bright or too even for the material, such as an electric blue or a lime green.
• A cotton bud with acetone, rubbed on an inconspicuous spot, picking up colour. Many dyes will not lift, so a clean bud proves nothing.

Our Aqeeq colour guide explains which colours are naturally common and which are usually dyed. See our black agate and Sulemani agate pages for how we describe them.

Plastic and pressed amber

Amber is fossil resin and very light. Plastics and resins copy it closely.

• Salt water float: dissolve plenty of salt in a glass of water, about two to three heaped spoons. Loose amber usually floats. Many plastics and glass sink. Rinse afterwards. Copal, a younger resin, also floats, so this test cannot separate amber from copal.
• Inclusions: perfect insects, flat leaves and round bubbles in neat rows are often signs of resin made to order.
• Pressed amber: small chips heated and pressed together. Look for a granular, flowing texture under the loupe.

Skip the hot needle test. It burns the stone and the smell is easy to misread. Browse our amber if you want to see the real material.

Reconstituted and imitation turquoise

Feroza is porous and soft, and the market is full of substitutes.

• Reconstituted turquoise is powder bonded with resin. It looks very even, almost like painted plastic, with little natural variation.
• Dyed howlite or magnesite is a white stone dyed blue. Dye often pools in the dark vein lines, which look painted on rather than grown in. Acetone may lift blue from these veins.
• Stabilised turquoise is real turquoise impregnated with resin to harden it. This is very common and acceptable when disclosed.

See our turquoise collection and the care advice in our soft stone guide.

Doublets and triplets

A doublet is two pieces glued together, often a thin slice of real gem on top of glass or a cheaper stone. Opal is very often sold as doublets and triplets.

• Look at the stone from the side. A straight join line around the girdle is the giveaway.
• Look for flat bubbles trapped along that line.
• The top and bottom may show different lustre or colour.
• Placing an unset stone in water can make the join easier to see.

Set stones are harder, because the setting can hide the join. That is one more reason to buy loose.

Where home tests stop

This is the honest part. Lab-grown stones have the same chemistry and properties as natural ones. A synthetic ruby or sapphire passes every home test in this article. So do many heat-treated or diffused stones, and so does a natural gem sold under the wrong name. Separating these needs a refractometer, a spectroscope, magnification by a trained eye, and sometimes advanced instruments.

Go to a gem lab when the price is significant, when a stone is sold with a big claim such as unheated or a famous origin, or when a home check gives you a doubt you cannot settle. Our how we check page explains what we look at before listing, and our returns policy covers you: if any lab finds a stone is not the natural gem we described, we refund in full including delivery.