Mini essays

Gemmology

Important to find out about a gem yourself. Sight-ID requires a lot of experience but is not often sufficient. Gem'ists confirm ID by thorough observation and by performing non-destructive tests. Need also to establish if a gem, for example a ruby, is natural or synthetic or if it has been heat treated or fracture filled. If the value warrants it a gem't may be able to establish the geological origin, where it was mined, by doing further tests. You may want to assess a ruby's durability, to ensure no incipient fractures exist that could jeopardise it. All this information will have an impact on the actual nature and value of the gem.

Consider the value of a green gemstone set in a ring

If you had to consider the value of a green gemstone set in a ring, what information would you need and why? First need to ID the green gem by observing and testing it. It could be an emerald, glass, tourmaline or something else. Then need to assess its nature. Is it natural, artificial or synthetic and has it undergone any treatments. These factors impact on the value. Then give a weight estimate. The heavier the more the value (as larger natural gems are rarer and therefore more valuable). Also look at the colour, clarity, durability and the quality of the cut and polish. [screen cut out at this point].

Estimate carat weight for a gem in a setting

Should be weighed on a scale but can estimate with reasonable accuracy. Need to know what gemstone it is; need a millimetre gauge to measure the length and width of the cut sone; ID the cutting style; apply a formula; make any necessary small corrections (eg: account for a slightly odd shape) - then get an estimate of the weight.

Cleaning

A client brings in a pendant set with a yellow gem described as a citrine. Says its vintage and asks you to clean it. You observe it / test to confirm it's a citrine. Using a 10x loupe you see a fracture. You make the client aware of the fracture and how it affects durability therefore they need to be careful when wearing it. As it's vintage don't use ultrasonic cleaning as it may damage it. You notice the close-back setting includes a foil. You don't use water or fluid to clean it as it might get trapped in the setting and tarnish the foil and disfigure the jewel. Advice is to clean with a lint-free cloth or soft brush.

Selling a treated ruby

Need to inform the client and explain the details. Customer may think the gem is of higher value than it is and if treated it will decrease the value but make it more affordable. Explain that the treatment is durable but not stable and to avoid cleaning with household cleaners or lemon juice as they might damage the gem.

Blue gemstone ring

• 1) assess gem for its nature – artificial , synthetic or natural. Any treatments. If unsure and may be of high value send to a lab
• 2) estimate weight in cts. Gauge quality. Check inclusions or external features that many decrease durability and desirability eg: fractures, chips, scratches
• 3) check resources to research current market value
• 4) ask customer about history and provenance, check for makers marks which could affect value