The blue zircons of Bokheo are the finest in the world. Only the stones from this area of northern Cambodia seem to acquire the intense blue colors that make them so famous. Across the nearby Vietnamese border, the stones just don’t seem to be able to get the same intensity.
Highway 7 from Phnom Penh to Stung Treng is paved and in good to great shape. A dirt road connects Highway 7 to Ban Lung (the capitol of the Ratanakiri Province). This road varies from good in the dry season to very bad in the wet season. Of course, I decided to visit Ratanikiri in the wet season and it was a long bumpy ride from the highway to Ban Lung. It is possible to fly into Ban Lung from Phnom Penh, but only in the dry season. This would be our base from which we would make our day trips to the mines.
While in Ban Lung, we stayed at the new and comfortable Kim Morakat Hotel. This hotel is located in town making it easy to walk through the markets and gem shops. I was surprised to see just how much fine quality cut zircon was available. Actually, I had never seen such good stones and never realized that zircon could be heated to such attractive colors. This trip was going to be a real learning experience!
Our first day out was our longest. In order to be back to town and avoid the afternoon rains, we had to be moving by 6 AM. This day Votha drove is car to Bokheo. This was no easy task as the road was in hideous shape. Amazingly, Votha was able to maneuver his car past the huge ruts and potholes. We were only high-centered a couple of times. Thankfully a Toyota Camry is not too heavy. The sixteen mile trip took about an hour and fifteen minutes each way.
In Bokheo we rented motorcycles and drivers that took us far out to a mining area that was producing stone that could be heated to an excellent color. The one-hour motorcycle ride took us down an impassable road and onto tracks into the jungle. Once we ran out of track, it was a twenty minute hike to the mine on the far side of Boloy mountain, where we found a group of miners working the slopes.
The mine in the jungle was located at;
13° 50.039’N by 107° 12.560’E
This stone was bought from the miners and later heated in Ban Lung
Our stay only lasted a few minutes as we had to begin the long trek back to Ban Lung. This was the most brutal day of the trip. The small motorcycles are not meant to carry two people across the terrain we traversed. My back would ache for the remainder of the trip. I guess it was a way to remind me that we had really been somewhere!
On the way back to Bokheo, we made a quick stop at a mining village just outside of town (13° 42.081N by 107° 11.752E). Here the miners would dig a vertical shaft about a meter in diameter and up to ten meters deep. The soil brought up would be sifted by hand for any stones. Horizontal shafts are dug when paydirt has been reached. This is the same technique seen all over the world when hand miners dig in dry alluvium/eluvium.
The mining village just outside Bokheo
Sifting the soil for stones
Back in Bokheo, we were offered low quality small crystals for about $20 per kilo. These would have been good for inclusion studies, but very few would have produced anything cuttable. We were told that there were other mines around, but they would be even more difficult to reach. The wise advice of the locals was to visit in the dry season!
Zircon by the kilo
I had purchased some rough from the miners that day. Once we had cleaned ourselves up from the long day, we headed out to see if we could find someone who would cook our stones for us. There are only a few stone heaters in the city and most of them wanted quite a lot for the service. Finally, we met Mr. Chhor Hour Kruy who was willing to help us with our project.
Mr. Kruy had been a gem dealer for many years and heating zircons for a dozen. We had “discovered” him through his wife who has a shop in the central market. I did not want to heat my rough that night since the quote was for treating 500 grams of rough and I was well below this quantity.
The next day, we again left early in the morning. This time we slept in a bit and did not leave until 6:30 AM. On this day, we started from Ban Lung on motorcycles. Our destination was the village of Baesrak (13° 36.880N by 107° 04.627E). This was a relatively new are for mining zircon, but it was producing quite a few stones.
This time our route was not as brutal as the day before. However, it was far from smooth. My back was already hurting from the pounding of the previous day. We had not been able to locate any larger motorcycles, so we again stuck with the little ones. The route was generally more level on this day, so we could travel at a higher speed. The drawback to traveling at high speed was that when we hit a hole - it hurt a lot!
One of the bikes had a flat as we approached a small village. This gave us a break while the inner tube was patched. Up to this point, we had been traveling through a large rubber tree plantation. Votha said that the whole thing was owned by a Chinese/Khmer man. He ran the place in the old style where he owned not only the plantation, but the town and shops where the employees live.
A quick patch of the inner tube and we were on our way again!
It was obvious that we were approaching Baesrak when we passed through fields that were absolutely full of the pits where hand mining had already occurred. The place looked something like a cross between a prairie dog town and the no-man’s-land between the trenches of WWI. Every square inch had been dug up!
A two legged prarie dog town
As we moved into town, we came across active pits in peoples’ yards. These pits were the same as before – a hole is dug straight down to about thirty feet to find a three to six foot gem bearing strata. The miners said that it takes about a day-and-a-half from starting a new hole until reaching the gem strata.
We walked through the town a bit and stopped to speak with some villagers. Apparently there was a big Korean mine nearby. They said that there had been a French videographer the previous year. Since coming home, I have tried to find if this video had been produced, but I cannot find anything.
Both Votha and I heard a familiar sound while sitting there. We had been hearing a gasoline water pump in the distance. I followed Votha down the hill through the banana trees. On the opposite hill, we could see the unmistakable signs of a larger scale mining operation. This claim was being operated by two men and one boy. They were using the standard high pressure hose to wash away the soil and send it down a flume. This time, they captured some of the gem bearing soil on a plastic tarp to search through at a later time.
Once we made it back to the motorcycles, we headed back through town to the Korean operation. On the way, I asked to stop at a building where some rough and cut stones were being traded. They showed us quite a few nice pieces. The owner had a very nice large zircon on his finder and a woman there had a necklace full of stones. We did not ask about the ring, but the woman said she would sell the necklace for $400. This seemed a bit high after visiting the gem dealer the previous night. I bought a single stone before we moved on.
Our arrival at the Korean mine was not welcomed. The guard there chased us off so I did not get any photos. However, we could see that they were using heavy equipment to excavate the soil and they had a trammel and shaker table to separate the gems from the tailings. This was by far the largest operation we saw.
We had considered visiting another site called Poom (Phum) Gop, but it was too far away and I needed a break from the rough motorcycle rides. Our day was far from over anyway since we still had to get back to burn the stones that we had collected.
The schedule that Votha had set was quite busy, so we did not even stop to shower before heading off to get our stones heat treated. I did not have enough stones to fill a crucible for the heating, so I bought 250 grams of small stones for $25 in order to fill up the crucible.
Selected stones before heating
Cooking the stones would only take about two hours after starting the furnace. The first step was to put the stones in a small crucible without any flux. Then a lid was places on the crucible and then sealed with cement. This was placed on the stove to dry the cement and drive the air out of the crucible.
Inner crucible
Sealing the crucible
Dying the cement
Next, this crucible was placed inside a larger crucible and the lid was again cemented in place. While the cement dried, the furnace was loaded with charcoal. Apparently the real secret to heating the zircons lies in the type of charcoal used. The identity of the proper wood was never mentioned. The crucible was placed on top of the column of charcoal and then the furnace was lit with a gas torch.
Inner crucible is inside this larger one
The furnace is loaded with charcoal and the crucible placed on top
A little more charcoal
The final step was to attach a chimney to the furnace so that the exhaust gases would not fill up the house. Heating rubies and sapphires requires a high temperature, and some sort of blower is used to generate a higher temperature. I did not see any type of blower around, so I guess that the charcoal just burned at a natural rate as the fire moved up the column of fuel.
The furnace is started with a gas torch (bottom)
All that was left now was to wait a couple of hours. This time was spent in the shop talking to Mr. Kruy. I asked about the history of zircons in the area, but he was not sure about the history, He believed that the original people in the area known as the Kola had first discovered the stones. Most of the Kola people had been killed by Pol Pot and his regime during the civil war.
The local zircon can be heated at a low temperature to cause the blue color. They could also be heated at a higher temperature for a longer time to get a yellow or orange. There are more zircon mines across the border in Vietnam, but they do not respond well to the heat treatment. These Vietnamese stones only acquire a very pale blue when heated. There is a constant risk for burners that unscrupulous dealers will sell the Vietnamese stones mixed in with local production.
A varitey of colors are possible by adjusting the heating process
Zircon production in the Bokheo area has been good for a couple of decades, but things are beginning to slow down. People believe that many of the good mining areas are now locked under the rubber plantations. The areas available to the small scale miner will be worked out in five years or so.
Official records show that licenses have been issued to two companies for mining zircon in Bohkeo District. Ultra Marine Kiri (Cambodia) Ltd. received a license in 2005 to mine in the Pating Thom village in the Ting Chak commune. The same year, Seoul Digem Cambodia Co. Ltd. received a license to mine in the Lomphat District of Ratanakiri.
Before long, the stones were ready. The crucible was brought out into the shop and the contents were dumped into a dish. The zircons had a very intense blue color while they were hot. This color became more subdued as they cooled. After they cooled completely, they had a color similar to fine aquamarine.
Fresh from the furnace
This blue color will change as the stones cool
Notice that these stones are a very different color than when cool
(Compare to photo at the top of the page)
It appeared that Votha and I had seen the highlights of zircon mining in the area and I was too sore for another outing. We decided to leave Ratanakiri the next morning and head back to Phnom Penh. There was a mysterious new mining area in the very south of the country and my schedule would allow us to make it if we gave up on further trips around Ratanakiri. I had heard that there are sources of amethyst and peridot in the area, but I was not able to investigate this.