This is an abridged excerpt from John's e-book "The Emerald Mountain" in which he recounts the year he spent in Colombia having set out on a quest to find an emerald that would solve his financial crisis. To read the full text, please visit his site

At the bus station are Indians, some with bowler hats and ponchos, who mill around never saying very much, negroes, the mestizos, and all in between. I've never seen so many beautiful women of all colours, shapes and sizes everywhere. There are many nuns and priests in several unconnected coteries, all preoccupied as they swarm around.

Many of Colombia's buses are extremely brightly coloured, and most have huge areas of iridescent and diffracting plastic film that shimmer in the sun with powerful chromatic colours. I like it. What I don't like is the No Smoking sign, especially as it will be many long hours before we reach Medellín. But the bus moves off, a dozen people light up, and my excitement increases with each moment as we leave Bogotá behind, but not before we pass mile upon mile of shanty town, and beyond that where only the cardboard dwellers can be seen.

As we descend into the valley between the Cordillera Oriental and the Cordillera Central, the vegetation starts to change and soon the last vestiges of the cold of Bogotá are obliterated as the bus begins to heat up like an oven.

We stop at unmarked points to pick more people up, and the conductor is kept busy as this small bus rapidly loses not only its empty seats but its gangway as well. I chivalrously stand for a woman, but am immediately pulled down by Leo who asks what I think I am doing? His normally confident face is clouded by incredulity. He insists we keep together, and take turns to sleep so as to minimise the danger of robbery and, what is more, we have paid for our seats. Very well, I think, the man is right, this is not England, and we have many hours to go before we get off this bus.

We start to climb the Cordillera Central, where we begin a long and tortuous ride along a thin ribbon of road that clings precariously to the mountainside. I watch in awe as the depth of the drop at the edge of the road is revealed. There would be quite simply no chance at all of survival if we went over. Seemingly, many buses do just that, and are never heard of again. The upper side of the mountain has equally as cheerful a disposition, as landslides, common in the wet season, assist the departure from this life of any bus, such as this one. Clearly, there is absolutely no point in worrying about this, so I get on with enjoying the view.

Sadly, passengers throw empty glass pop bottles out of the window without regard. I wonder if they would be equally as carefree if our bus tyres were to blow-out at speed on the edge of the mountainous precipice.

Some time later, the uninterrupted broad vista of Nature takes a kick in the goolies as an unmistakable sign of the times rears its very sad head. It is a large red hoarding placed in the middle of nowhere advertising the virtues of a particular brand of cigarettes. In an area devoid of habitation, and indeed some way off the road, you have to ask "Why?"

On the facing mountainside we can see the road we have already driven down. It is some four to five miles away, as the condor flies, yet to cover this distance, we have spent hours hugging the steep slopes. When we finally reach Medellín, I marvel at its location in what seems to be the bottom of a huge rocky cauldron. We are well above the city and can look down, almost as an aircraft passenger, at the myriad streets and buildings. High above Medellín, a mirror-smooth pale purple and blue ghostly lake of air seems to extend all the way down to the city. It is the curse of smog. The pollution is trapped in this vast cauldron leaving the people of Medellín smothered in their own exhaust fumes.

Our exact moment of entry into this sea of smog is clear as the bus descends, but no-one seems to notice. Yet for me it is palpable, and it is very soon afterwards that the acrid smell and taste envelops me. My eyes and throat feel tainted and irritated. It's horrible. How can anyone be fit and healthy in that?

We are in Medellín for only two hours, and stay within the confines of the bus waiting for the bus to Turbo. When it does come, I am horrified at the two bald tyres at its rear. As we set off on the second leg of the journey we soon return to the ribbon mountain roads, and I try not to think about the tyres.

A change of scenery

When we finally reach Turbo, our first job is to find a hotel, so that Leo's immediate self-imposed task of finding more herb can begin. Turbo is a wild, wild place, like something straight out of the early frontier towns in the US. Guns go off in the main streets and there are open bars with the distinctive swing doors so beloved of western films. I sense a real undercurrent of wanton violence here, even more than in Bogotá. I am uneasy. Leo feels this and tells me not be afraid. The air in the main street is full of the smell of basuco. This must surely be Mafia country. Everything is loud and there are commotions outside the cinema, which is showing the same old type of jungle-warfare film that is guaranteed to be crammed full of gratuitous violence. More or less every male carries a machete within a scabbard with long flowing colourful leather thongs, and many carry guns on open view as well.

We find a hotel and immediately stumble across hassle. A man close to our room sends his wife to entice us with lots of sex if we will come and join the basuco party in their room right now. From behind our locked door, Leo booms out an immediate and irrefutable get lost message, and I finger my knife nervously. Admittedly, I could certainly have enjoyed some wild sexual abandonment, but the thought of basuco and its effects puts me off and, like Leo says, all the man wants is our money and he will take us to the cleaners and then we really would be in trouble in these parts. We wait for a response from the addict, but there is none so we eventually relax.

The toilet is blocked and there are no adequate words for the stench in this tropical temperature. Unfortunately, the shower is located in the same area.

The next day finds us in the small DAS (Departamento Administrativo de Seguridad - spoken of by many as the secret police, but from where we must get our exit visas) office with its large, slowly rotating ceiling fan. The floor is smooth, hard and polished, and lizards flit over it with their peculiar jerky motion. The sun is bright and fierce outside, and its light is still dazzling in here. We find there is no joy to be had for a couple of hours since the officers are out on a job. Leo goes to score more weed, and scorns my exhortation to take care given our position inside the DAS office.

I too go for a walk locally, but my intention is just to pass the time. There are not many houses near here and I am just wandering when I hear a pack of dogs in the near distance suddenly barking excitedly. My guard goes up automatically at the same time as the indoctrinated thought calls out, "Rabies is endemic in Colombia". I note that the barking is getting louder, rapidly. There sounds to be at least four or five of them, and there is an unmistakable flavour of attack surging through the massed barking. I am vulnerable without my jungle boots - flip-flops are hardly the best defence against a pack of dogs either for kicking or running. Indeed, running is simply not viable and I discount it immediately, leaving the way open for a full-blown fight. They seem to be approaching through the waste overgrown land to my right, so I adopt the most serious stance I can for the maximum expression of pure hostility. Adrenaline pours into my bloodstream. My walking stick is poised and throbbing, ready to splinter bones wholesale, and my facial expression asks the big question of my imminent attackers who now cannot be many metres away, their approach still hidden by the long grassy growth. There is a path leading out of this tall vegetation . . . any second now, . . . deep breath, . . . I summon all the energy and determination I can . . . throttles wide open, and here they come, paws scrabbling and kicking dirt as they angrily bank round the corner showing masses of ugly bared teeth, and we are now face to face.

The image I present to them is a combination of delighted surprise, resolution and full-blown naked aggression slapping fearlessly in their faces and communicates instantaneously; they immediately turn tail as one, fully psyched out, running equally as fast in retreat, their snarls turned into yelps.

A near thing. If it had gone to a messy battle, I would have undoubtedly suffered injury, although I think I would have certainly killed two or three of them. As it is, I have escaped without a scratch, and that means I need not be subjected to the horrific regime of anti-rabies treatment. The adrenaline takes a fair while to subside so I breathe deeply and slowly and try to calm myself down.

I am back to normal well before Leo returns. Finally the paperwork is dealt with and we are now free to leave Colombia. The launch will leave tomorrow at 08.00, and we must be ready or else face another few days here, which we neither can afford nor want.