How many prawns make a sapphire?

THERE COMES a point in every woman's life when the acquisition of a jewel, a serious jewel, becomes not merely appealing but imperative. I reached that point shortly after breakfast last Friday morning when, passing from the hotel dining room to the cliff-top terrace for a better view of Indian Ocean shipping lanes, I noticed a discreet but attractively lit glass cabinet displaying local gems in one corner of the lobby. I paused.

"Come quick or you will miss the supertanker," said Mr Pog tugging at my elbow. "You do realise that a vessel that size takes 12 miles to stop don't you?"

To be honest I didn't, but then, until I met Mr Pog the previous day by the hotel pool, I was equally unaware that there are 27 different kinds of banana in Sri Lanka and 83 varieties of snake of which only five are poisonous, and that if my husband were to invest, say, $100,000 setting up a prawn farm in Negumbo - Mr Pog had a friend with lagoon rights affording excellent marine harvest opportunities in Negumbo - he would certainly make 300 per cent of his money within six months.

"You look at the tanker, I'll look at the sapphires," I said and then remembered that Mr Pog, although Sri Lankan born and bred, had a Dutch grandfather (hence his curious name) from a diamond broking family in Amsterdam. "Unless, that is, you know anything about gems..."

Mr Pog cast a cursory glance at the contents of the cabinet, murmured something about tourist rubbish, and said that if I were really looking for an investment I should buy not sapphires but alexandrine. It just so happened that he had a friend who could supply me with a piece of alexandrine weighing up to 50g which would certainly quadruple in value within...

Alas, I shall never know. One minute Mr Pog, charming, educated, attentive, was there beside me. The next he was being flung out on his ear with the duty manager hissing that if he ever caught the bounder on his hotel premises again he would call the police. "But I thought he was the entertainments director," I said. "He told me he was the inspiration behind your splendid New Year's Eve celebrations last night."

The duty manager smiled politely and expressively, by which I mean that his expression fell somewhere between "some mothers do have 'em" and "there's one born every minute".

It was at this point that I knew I should have to save face by acquiring a serious jewel. There was just one problem - I know absolutely nothing about precious stones. Then again, who does?

My mother knows all about rubies because she's Burmese. When she was at the mission school in Moulmein before the war, she swapped her most precious possession, a matchbox full of cotton wool, for a set of fivestones belonging to a girl called Nancy whose father worked in the ruby mines at Mogok. Each fivestone was a tiny ruby.

She was dismissive of my first engagement ring, an avant garde piece by an award winning Chelsea designer featuring three rubies set asymmetrically around a diamond. A ruby, advised my mother, never plays second fiddle to a diamond. It should always be the centrepiece. Not that it mattered much, she added witheringly, since these rubies were far too red and shiny to be proper Burmese rubies and if they weren't Burmese they didn't count.

The only advice of any consequence my oldest daughter's godfather offered - it came together with a white prayer book on the occasion of her First Communion - was that before she went to bed with anyone she should first look under the pillow to check for the jewel.

Ah yes, but say there was a jewel and 12 hours later in the cold light of morning those emerald ear clips turn out to have cost less than the price of a prawn sandwich? When you buy a gem from a reputable jeweller's, they give you a certificate of authenticity. The chances of finding one under your pillow are slim.

How much are those earrings? I asked the hotel assistant. "22,000 US dollars," he said. "Or if we are talking sterling that is roughly pounds 15,000. These are yellow sapphires set in handwoven gold, a particularly lovely piece if I may say so."

Let's work this out. If my husband invested pounds 5,000 in a prawn farm, in six months time he would make pounds 15,000 and I could get the earrings...

I wonder what Mr Ratner would make of the arrangement. I'm sure Mr Pog would approve.