Our precious stones

Historically, only four gemstones are classified as precious stones: diamond, sapphire, ruby and emerald. All others — tsavorite, spinel, tourmaline, aquamarine, tanzanite, garnet — are known as semi-precious stones. This distinction is today largely historical and commercial: the rarity and quality of a fine semi-precious stone can surpass those of a standard precious stone.

Authenticating a precious stone requires a gemmological certificate issued by an independent laboratory. The internationally recognised laboratories are GIA, SSEF, Gübelin and GRS. Every precious stone sold by Bonnot Paris is delivered with its certificate of origin and treatment.

Sapphire is the most sought-after precious stone for engagement rings after diamond, prized for its hardness (9 on the Mohs scale) and the enduring stability of its colour. Ruby and emerald are equally prestigious choices. For a more accessible budget without compromising on quality, tsavorite, spinel and pink sapphire offer excellent alternatives.

Direct sourcing in the country of origin allows us to eliminate intermediaries, guarantee traceability of the stone from the mine, and offer outstanding value. Bonnot Paris has offices in Sri Lanka, Jaipur and Bangkok to select each precious stone at source.

A stone dealer and jeweller combines two trades: the buying and negotiating of precious stones as close to the mines as possible, and the creation of jewellery pieces. This vertical integration allows Bonnot Paris to command the complete value chain, from rough stone to set jewel.

It depends on the treatment. Heating sapphires and rubies is a practice the market has accepted since Antiquity and affects value only marginally. Modern treatments, however — beryllium diffusion, lead-glass filling and irradiation — artificially alter a stone's colour or transparency and durably diminish its value. These treatments must by law be declared on the certificate.

Bonnot Paris will under no circumstances offer for sale any precious stone that has undergone beryllium diffusion, lead-glass filling or irradiation. The house consistently favours unheated stones certified by an independent laboratory, and accepts heating only when it is traditional in nature and clearly stated on the gemmological certificate.