Seru Francisco Jobo - more to the South

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Seru Francisco Jobo 20160310 022 smallOn Thursday March 10, 2016 the archaeology sleuths went once again to the Seru Francisco Jobo for further investigation. The previous weeks we had searched the Eastern slope and a small part of the Western slope (Jerimi side) of this mountain for traces of manganese mining. Apart from the two already known tunnels, one accessible, the other closed, we found several previously unknown locations where surface mining for manganese was done. This led us to the conclusion that the two tunnels were not actual the result of mining but are trial pits to determine if manganese was also present inside the mountain. Apparently this was not the case in sufficient quantities and that explains why there are no more tunnels in the mountain. Almost everywhere else in the world manganese is found in surface mines. Apparently that was also the case in Curaçao, although not in such quantities that profitable mining was possible. The mines were apparently abandoned after one year.

What we wanted to investigate during this trip is if there is also manganese on the Southern slope of the Seru Francisco Jobo and if there is manganese on the Jerimi side of the mountain, where the processing plant is located. The last time that we checked the Jerimi side (last week) we didn't find any traces of manganese there.

We parked our cars at a more Southern location and started our hike up the hill. We crossed a dry-stone wall and went on to the surface mine that we found during our last week's trip. From there we went in Southern direction. We found manganese almost everywhere along our track till we reached a "corner" where we had to continue to the West while walking on the Southern slope. From there on the amount of manganese became less and less and also the the kind of rock changed. Everywhere where we found manganese the rock is reddish in color; that color gradually disappears around the corner; there we find the more traditional Knip formation rocks without inclusions of manganese. So apparently the manganese was deposited in the part that currently forms the Eastern side and a small part of the Southern side of the Seru Francisco Jobo.

We continued our hike in the direction of another top of the Seru Francisco Jobo. There we looked for a Kadaster measuring point but didn't find any. Not so strange because we already found one on another top of this mountain, but we wanted to be sure.

From there we went back following the dry-stone wall till we reached the known tunnel. From there we followed the path back to the dirt road; we followed that road back to our cars. That concluded this last hike on the Seru Francisco Jobo.

Our conclusions are that most probably the tunnels were trial pits and not the result of real mining activity and that the actual mining took place in surface mines of which we found several over a large area of the Eastern slope of the Seru Francisco Jobo. The transition takes place on the adjacent Southern slope where the mangane containing rocks gradually disappear.We didn't find manganese on the Western side (the Jerimi side) of the mountain. Most probably the processing plant and other (Newtown) buildings were placed on that side because it was easier to put them there. It is clear that the manganese mining was not a success because the buildings were abandoned after 1 year.

I took several rocks during the previous trip and I took the time to study them in more detail. Fred already had told me that the manganese was not conductive even though it is a metal. I did the same test and confirm that there is indeed an immeasurable high resistance between two points in the continuous manganese deposit. I did a similar test with another rock that had a strange looking thick crust of very dark material. A closer look revealed that there were lighter colored mottled parts in this rock. Similar measurements on this rock showed a different result. The darkest material has an immeasurable high resistance, but the lighter gray material has a rather low resistance of less than 1 kOhm measured 2 centimeters apart. Another interesting fact is that the same low resistant is measured when the probes are placed on two spots that are separated by the dark material. Apparently the lighter colored material continues underneath the dark crust. The lighter colored material could be an iron ore. A picture taken with a macro lens from this lighter material shows tiny crystals.

Pictures from our hike can be found underneath.