P is for Palong

by Maganjeet Kaur

The image below is that of the palong, installed at Gallery C. A palong is essentially an elevated sluice-box supported on wooden scaffoldings. It is an important component in opencast tin mining (both dry and gravel-pump), a mining method exploiting tin-rich alluvial soil.

Palong in Gallery C, Muzium Negara. Image credit: Maganjeet Kaur

The first step in this method is to remove the overburden, as it does not contain any tin. This used to be done manually using shovels until tractors took over; an alternate method uses water jets to strip away this layer of the soil. Next, using monitors, water is applied at high pressure to break down the tin-bearing rock, and the resultant slurry washes down to a sump (bottom of the pit). The mining pit is intentionally made steep to ease the flow of the slurry.

The slurry is then pumped up to the palong by means of a gravel pump, which is housed in an attap shed just above the sump. The gravel pump, originally used in gold mining, was adapted and improved by Australians for the mining of tin. A company based out of Victoria, Australia introduced gravel pump technology at their new tin-mining venture in Sungei Raya, Kinta Valley, in 1907. Gravel pump mining caught on rapidly and was employed by Chinese and European companies.

Tin mine at Kampar, Perak c. 1910. Notice the steep walls of the pit and the slurry in the sump. Image credit: Leiden University Library, Public domain, via Wikimedia Commons (photographed by C. J. Kleingrothe).

The image shows an attap shed housing the gravel pump in the foreground and jets of water from monitors in the background. Image credit: Yap Keam Min, http://dspace.unimap.edu.my/handle/123456789/13900

Role of the palong

The palong is considered the most important component of the opencast tin mine as tin is recovered here. Thus, it has to be well designed to avoid wastage. The design must account the gradient of the palong. A gentle slope may result in improper flow of the slurry while a very steep slope, where the slurry flows down fast, results in poor recovery.

The slurry forced up the palong by the gravel pump first goes through a revolving screen that removes large pieces of stones and gravel. As the slurry flows back down the palong, it is agitated by transversely placed wooden bars, which trap the heavy tin ore. The recovered tin is transported to a washing plant known as a tin shed. After washing, the ore is stored in this shed until it is ready to be transported to the smelting plant.