Part of Werners skill is knowing exactly what price to pay for any given stone an talent honed from years of experience examining thousands upon thousands of gems.
But Werner also has a little something extra which sets him apart from most of his rivals; he has a feel some say a sixth sense of the value of a stone.
Its easy to buy expensive and impossible to buy too cheap. You have to get to know exactly how much to pay, he said with the sparkle of a man with a renowned eye for a bargain.
His obsession with buying also gives him another edge over his competitors, who are compelled to delegate in order to cover all the myriad sources. Werner refuses to do that. It has to do with the confidence of the people who are selling me the stones, he explained.
The bright-eyed Swiss man spends much of his time in Madagascar the huge island nation in the Indian Ocean off the east coast of Africa where he has built up the trust of local people who now rely on him to offer a tough, but fair price for their finds.
I'm not trying buy really very cheap because it is bad for my reputation. If I offer them a fair price, many people get more than they expect, he said.
A sense of value is clearly key to Werners work, but experience has also been vital to that, and as with many professions, the secret is to work very hard, he said.
Indeed, when he is in a mining area, he will work relentless from 7am to 9pm, quickly but methodically examining gemstone after gemstone presented to him by an eager queue of Africans, and then working late into the night to sort his days purchases.
If someone wants to copy me, they cant it's never the same, he said.
His job is made harder by the need to keep track of the changes in market valuations of gemstones, in markets which can be quite volatile for some types of stones.
Its a continuous process and the market also changes. Its a little bit like sport, he quipped.
But he added: Its a very brainy sport because every stone is different and every stone has a different price. It's got to fit the mesh, like a picture.
Indeed sport is the key to what drives the intriguing Mr Spaltenstein his surname means stone splitter in German.He is a man of simple tastes, with no desire for the trappings of wealth; neither is he searching for the biggest or brightest gems in the world.
My objective is to be a good buyer. If I am very correct with my estimations there is a satisfaction, he admits, adding that he may make one or two mistakes on price out of a hundred purchases, where others may fall down on ten percent of occasions.
Whilst Madagascar is currently the focus of Werners work, he has also spent much time in Tanzania and Kenya, and regularly shuttles back and forth to the gem dealing and cutting centres of Thailand. He is under no illusions about the dangers of his work, however.
I have a very interesting job. I hope I survive I am doing a very dangerous job, he admits, with a glint in his eye.
Given the precarious value of Madagascar currency exchange rates, he must transport 40kg of local money across the country in order to buy 7kg of stones, and his ability to inject capital into the economy has helped give Werner a buying edge, and benefited ordinary Africans in a very direct way.
Except for brokers and small merchants, noone has money. They are living from hand to mouth, said Werner.
He is at the coalface of the gem business a go-between bridging the African nations, which have little inherent use for gemstones, and the West, which prizes their precious jewels.
Werne's happy position enables an African to buy land, or perhaps treasured oxen a traditional symbol of wealth, while at the same time supplying Americans and Europeans with their own traditional symbols of riches, gems.
Its a real gold rush here, he said. I may have 100 or 200 people selling to me. It doesn't matter if they are rich or poor; anyone can show me their stones and gets a fair offer. If someone has the luck to find a good stone he should get a good price.
Buying is Werners life, and he admits he had no patience for selling. Selling is a very slow process, he explains. He is no sentimental about his acquisitions, but he concedes he is attached to the knowledge of the market associated with them, hence the need to keep track of their resale in order to hone his valuations.
Its just got to do with whether I was right with my estimation. I try to be as good as possible, and thats why I need that feedback on supply and demand, he said.
Being aware of subtle changes in the market is crucial to the business. The price of tanzanite, for example, went up and down every year for quite a whole.
I miscalculated a little bit on the tanzanite. It was very expensive, the price came down, I bought it, we made very good business, then the production and demand fluctuated around US$250, and then went down to US$120. I was buying again and it went down to US$80 and it backfired. Now its US$300US$400. That is the most unpredictable stone as the supply is so limited.
And as Werner adds: Everything depends on the supply, and I don't know what they are going to find in the future.