An Introduction to Gemstones
Before purchasing a coloured gemstone, it is essential to understand that not all gemstones are the same. Gemstones differ significantly in origin, treatment, and value, and misunderstandings can easily arise if these distinctions are not properly explained.
Main categories of gemstones
Natural gemstones
Natural gemstones are formed by geological processes in nature without human intervention. Their value is determined by rarity, colour, clarity, cut, and carat weight.
Synthetic gemstones
Synthetic gemstones are created by man but have the same chemical composition, crystal structure, and physical properties as their natural counterparts. As long as a gemstone is clearly disclosed as synthetic, its value is substantially lower than that of a natural gemstone.
Today, most types of coloured gemstones can be produced in laboratories and are often marketed as “cultured” gemstones. Synthetic diamonds are also available and must legally be disclosed as laboratory-grown, man-made, or synthetic.
Treated natural gemstones
These are natural gemstones whose colour or clarity has been enhanced by human intervention. Treatments must be disclosed, as they can affect value, durability, and long-term appearance.
Imitation gemstones
Imitation gemstones are made from materials such as glass or plastic to resemble natural gemstones. They are inexpensive and generally easy to identify under magnification.
Why gemstone identification matters
Gemstones can differ widely in value and are sometimes misrepresented through lack of knowledge rather than intent. For this reason, it is strongly recommended to purchase gemstones accompanied by an identification or grading report issued by a qualified gemmologist.
Common gemstone treatments
Bleaching
Chemicals are used to lighten or remove colour. Pearls and ivory are commonly bleached using hydrogen peroxide.
Dyeing
Porous minerals readily absorb dyes to improve colour. Lapis lazuli, jadeite, cultured pearls, agate, and turquoise are frequently dyed.
Cavity filling
Surface-reaching cavities are filled with glass or plastic, particularly in rubies and sapphires.
Colour impregnation
Resins or waxes are drawn into cracks or pores under vacuum to stabilise or enhance colour.
Fracture filling
Fine fissures are filled with oil, resin, or glass to improve clarity. Emerald and ruby are the most commonly fracture-filled gemstones.
Heat treatment
One of the oldest gem treatments, heat can alter colour and inclusions. It is widely used and often stable when properly disclosed.
Irradiation
X-rays or sub-atomic particles alter a gemstone’s atomic structure to change colour. The vivid blue colour of many topaz gemstones is the result of irradiation.
Lattice diffusion
Elements such as titanium or beryllium are diffused into a gemstone’s crystal structure at high temperature to alter colour, commonly in sapphires and rubies.
Sugar and smoke treatment
Used mainly for opal, sugar or smoke darkens the gemstone’s appearance through carbon deposition.
Surface coatings and painting
Thin coatings or painted surfaces may improve colour but are usually unstable and often associated with fraudulent intent.
Reconstitution
Low-grade gemstone material is crushed, dyed, and bonded into a solid mass shaped to resemble a natural gemstone.
High Pressure / High Temperature (HPHT)
HPHT techniques are used to alter or remove colour in diamonds and must always be disclosed.
Our commitment
Rest assured: All gemstones from Prins & Prins are supplied with a grading or identification report issued by a qualified gemmologist. Transparency, disclosure, and expertise form the foundation of our approach.