WHEN a leading scientist writes that ``the most remarkable gemological instrument I have ever seen is Alan Hodgkinson's eyeball'', it is immediately clear that the person quoted must have an intense knowledge for the identification of natural and synthetic stones.

Not surprisingly, world-class gemology expert Alan Hodgkinson's CV is as glittering as the gems he has been identifying over the past 40 years, and he has made the training of others in this field his life's work.

He was appointed as the first Group Training Officer in the Jewellery Trade back in 1969 and three years later, after setting up his own jewellery business in Glasgow's south side, he created the first UK practical gem identification courses.

By his own admission, he loves the sound of his own voice - which is fortunate, since he has lectured for Glasgow University, for De Beers and the International Gold Corporation; and has run diamond and gem identification lecture tours in South Africa, Sri-Lanka, India, Germany, the US, Singapore, Ireland, Australia, New Zealand, Canada and Hong Kong.

Every year he is invited to be the major keynote speaker and/or lecturer at some of the world's major gemology conferences, and he continues to run residential two- and three-day gem identification courses.

As prolific writer - author of Visual Optics: the Hodgkinson Method - he has produced and delivered papers on gemology all over the world. He has also invented a variety of gem-testing instruments which have become vital at a time when the jewellery trade is faced with threats on all sides.

Apart from increased competition from non-traditional outlets with warehousing, discounting and ``wholesaling'', there is the increasing threat of ultra-clever synthetic gems entering the market, undetectable to the untrained eye.

``When the public go to the jeweller, they look for a measure of trust and that t hinges on the jeweller being able to reassure,'' he says. ``That is more difficult today because we have passed from the age of imitation gemstones that have been on the go for 4000 years - the fake turquoise in Tutan-khamen's tomb dates back 3500 years - through to the space age where crystal-growing techniques are growing gemstones.

``The first synthetic rubies were created in the 1880s but today there are more sophisticated crystal-growing techniques which include the features in natural stones. I have worked for the past 25 years building information on this.''

According to Hodgkinson, the new synthetic gems are so clever that they have inclusions in them. It takes six months for them to grow a centimetre and they cost around #200 a carat, compared to around #5000 a carat for a fine natural ruby.

As far as consumers are concerned, it is a minefield. They can now choose from a spectrum of imitation red glass, inexpensive synthetic rubies, new flux-grown rubies, poor-quality natural rubies, or fine ones. The biggest problem now facing the jewellery trade is synthetic diamonds. First grown in 1955 for industrial purposes, the synthetic diamond is not in the shops yet but is being prepared for technology and industrial purposes, and countries like Russia and Japan are among the many involved in growing them.

``Once they are in the jewellery trade they are very hard to detect,'' says Hodgkinson. ``The capital investment in growing them is very high but competition keeps the price down. This growing of synthetic gems is the biggest challenge facing the trade.''

For some time he has been heavily involved in working out a defence against the synthetics - instruments of detection which are essential for jewellers and valuers if they are to retain their reputations and the trust of their clients.

He says one of the most pleasing developments in recent times has been the effort by the jewellery trade to professionalise itself by developing a body called the Registered Valuers. Anyone wishing to register as a valuer today must be qualified; something that was not enforced in the past.

Hodgkinson was instrumental in starting that movement towards qualification in 1971, as the first group training officer for the jewellery trade in the UK; but it was a tough task.

``Glasgow led the way, ahead of the whole of the UK,'' he says. ``The city's well-known jewellers realised that as individual units they could not afford a training officer, but as a group they could. So I came down from Aberdeen to start the ball rolling. ``We were funded/grant-aided by the Distributive Industry Training Board but within two years they told us they were pulling out and that we would have to be self-financing. The trade was not up to that.''

At that point, as a means of funding his training programme, Hodgkinson opened his jewellers' workshop and gem-testing lab at Clarkston, built on ``trust and a prayer''.

The business grew to incorporate manufacturing, repair, design and valuation, and has been very successful. He has since trained three young people to run it, which allows him to concentrate on his first love - identification of gems.

Having created a funding base, he approached the Gemology Association in London, which had been offering theory-based qualification since the 1920s, and suggested his hands-on practical modules.

When it showed no interest, he returned to Scotland and started the first of his ``Two Day Practical Gem Identification Course''. They were very successful and almost adopted by the association. In 1978 he delivered a paper -Visual Optics - to the Gemology Association, putting forward the non-scientific Hodgkinson Method of identifying gems by using the naked eye to assess reflection, refraction and dispersion of light.

The academic world howled him down but Drs Hanneman and Nelson, internationally recognised scientists, rose to his defence and together they refined the technique which is now widely accepted.

Twenty years on, the gemology academics listen and learn.