THE CHEMISTRY OF DIAMOND RINGS Diamond rings are synonymous with engagements; diamond itself is an form (allotrope) of carbon, but other chemical elements can impact on its appearance. Here we look at ‘the 4 Cs’ and their chemistry links, as well as some of the metallic elements that help to make up the ring itself. DIAMOND CUT DIAMOND CARAT 0.25 Ct 0.50 Ct 0.75 Ct 1.00 Ct 1.50 Ct 2.00 Ct 4.1 mm 5.2 mm 5.8 mm 6.5 mm 7.4 mm 8.2 mm SHALLOW IDEAL DEEP Top: weight in carats; Bottom: approximate diameter in millimetres. Diamonds not shown to scale, but are in proportion to each other. The cut of a diamond affects how well it reflects light. Diamond carat measures mass; one carat is equal to two Too shallow or too deep and the reflection of light is poor, hundred milligrams. Diameters are approximate, as they so the diamond seems to sparkle less. vary depending on the cut of the diamond. DIAMOND COLOUR DIAMOND CLARITY RING COMPOSITION WHITE GOLD Au 75% Pd 10% Ni 10% Zn 5% Rh PLATE D → F G → J K → M N → R S → Z F → IF VVS1/2 VS1/2 SI1/2 I1/2/3 ALMOST FAINT VERY LIGHT LIGHT COLOURLESS FLAWLESS OR VERY VERY VERY STERLING SILVER COLOURLESS YELLOW YELLOW YELLOW SLIGHTLY INTERNALLY SLIGHTLY SLIGHTLY INCLUDED INCLUDED FLAWLESS INCLUDED INCLUDED Ag 92.5% Cu 7.5% Pt TRACE Ge TRACE Zn TRACE POTENTIAL ELEMENTAL IMPURITIES GAINED DURING DIAMOND GROWTH 7 5 1 14 15 28 27 YELLOW GOLD Compositions given are NITROGENN BoronB HYDROGENH Sisilicon PHOSPHORUSP NiNickel Cocobalt TYPE Ia TYPE Ib TYPE IIa TYPE IIb approximate for a typical 0–0.3% N 0–0.05% N 0% N B impurities Au 75% Cu 12.5% Ag 12.5% alloy, and can vary slightly (clusters) (diffuse) Most diamonds have some imperfections. These can be internal or external, and include chips, scratches, carbon The colour of diamonds is influenced by impurities. Nitrogen spots due to carbon not completely crystallising when the The ring itself can be fashioned from a variety of metals. impurities can give a yellow hue, whereas boron impurities diamond was formed, or artefacts due to the presence of Alloys of gold and silver are common, but platinum rings and give much rarer blue diamonds. Type Ia are most common. other impurities in the diamond. palladium rings are also popular, and more durable. C © COMPOUND INTEREST 2015 - WWW.COMPOUNDCHEM.COM | Twitter: @compoundchem | Facebook: www.facebook.com/compoundchem This graphic is shared under a Creative Commons Attribution-NonCommercial-NoDerivatives licence. BY NC ND.