(IDEX Online) - Lab-grown diamonds should be sold with second-tier reports, giving details of their manufacture, rather than 4C gradings, says CIBJO, the World Jewellery Confederation.It is keen to preserve the distinction between manufactured diamonds and natural stones - for which "rarity is a critical factor".CIBJO has released a Laboratory Grown Diamond Guidance document, the final stage of a two-year process to standardize the lab-gown sector and boost consumer confidence.Lab-grown reports should include the name of the manufacturer, the production batch, country of origin, method of manufacture (HPHT or CVD), and information about any treatments and processes the diamond has undergone - all of which reinforce the message that the stone was made, not mined.If the 4Cs are used to describe the physical characteristics of lab-grown diamonds, the letters "LG" should be placed as a prefix before color and clarity."The laboratory-grown diamond sector and natural diamond sector operate according to different business models with the relationship between colour, clarity and weight, on the one side, and rarity on the other, which exists with natural diamonds, not relevant with laboratory-grown diamonds, where colour, clarity and weight are subject to the control of the laboratory-grown diamond manufacturer," said the CIBJO board of directors in a statement.Generic pic of a lab-grown diamond