The geology and mining industries of Johore
E. S. Willbourn, Senior Geologist of the Federated Malay States, published this comprehensive geological survey of Johore in 1928, synthesising fieldwork conducted by himself, G. R. Fulton, and H. E. Savage between 1922 and 1927. The article establishes the structural geology of the State—demonstrating that its haphazard mountain groups are the eroded remnants of Mesozoic granite intrusions along anticlinal axes—and assesses the economic potential of its tin and iron deposits, concluding that Johore’s mining future lay primarily in the Bukit Medan haematite mine rather than in tin.
Summary
Willbourn’s central geological argument is that Johore’s topography, unlike the linear granite ranges of northern Malaya, reflects incomplete granite intrusion along the same structural axes. The State’s mountains are isolated bosses of Mesozoic granite that never filled the full length of their anticlinal positions, so erosion left them as scattered groups rather than continuous ranges. The pre-granite sedimentary rocks—Permo-Carboniferous Raub Series phyllites and Triassic quartzite-and-shale—carry a strike of N.N.W. by S.S.E. to N.W. by S.E., confirming their structural continuity with the Peninsula as a whole (pp. 5–6).
A significant revision to earlier interpretations is Willbourn’s demonstration that the volcanic rocks of the east coast and China Sea islands are pre-granite in age, not Tertiary as previously supposed. Evidence from Pulau Tioman, where volcanic rocks have been heat-metamorphosed by the granite, and from Pulau Nanas, where tuff contains fragments of a Palaeozoic granite torn from a volcanic vent, compels reclassification of these rocks into the Pahang Volcanic Series (pp. 8–12). The columnar rhyolite of Pulau Keban, once taken as proof of post-granite age because its vertical joints were untilted, is reinterpreted as a hypabyssal plug too rigid to have been affected by folding.
The mining assessment is sober. All tin workings in Johore, with one exception, are in shallow soil or river-deposits on weathered granite margins—short-lived operations that will be exhausted as the thin karang is worked out. Willbourn identifies the high-level alluvium as the most promising untested target, since in Perak’s Kinta Valley this formation contains substantial tin reserves, and Johore’s equivalent deposits, up to 200 feet thick, have never been properly bored (pp. 17–20). The Bukit Medan iron mine, by contrast, is a major industrial asset: a single isolated hill of haematite and kaolin-like clay producing 30,000 tons monthly at 64 per cent iron, supplying roughly 40 per cent of Japan’s total iron and steel consumption (pp. 20–26). Willbourn’s provisional theory—that the ore formed by hydrothermal alteration of a rhyolite plug, with silica removed and haematite deposited—remains unconfirmed but suggests potentially large underground reserves.
Key Findings
- Bukit Medan (Sri Medan) iron mine: 30,000 tons/month of haematite assaying 64% Fe; total output rose from 18,536 tons (1921) to 231,000 tons (1926), with an estimated 350,000 tons for 1927; represented approximately 40% of Japan’s total iron and steel usage (pp. 20–22).
- The mine’s tunnel, 1,044.2 feet long, proved 670 feet of primary haematite and clay in situ; a single bore-hole in swampy ground bottomed on metamorphosed shale at 123 feet, the only non-haematite rock encountered (pp. 24–25).
- Tin mining in Johore was entirely small-scale: the largest operation (Bukit Pelali) produced about 200 pikuls/month from lombongs in a valley half a mile long; Ulu Madek’s gravel-pump mine peaked at 100 pikuls/month with 200 coolies before ceasing work by 1927 (pp. 18–19).
- Pulau Aur, the most easterly island in British Malaya (about 50 miles offshore), yielded cassiterite in beach sand assaying 0.6% metallic tin, but deposits were too small and low-grade to be workable; the island is built of hornblende-granite and syenite, an unusual assemblage for tin production (p. 19).
- High-level alluvium in Johore is probably over 200 feet thick (by analogy with Kinta, Perak) and has never been tested for tin by deep boring; Willbourn recommended bore-sets capable of reaching 150–200 feet (pp. 14–15, 20).
- The altered rhyolite at Kangkar Senangar and Bukit Pengerang has a chemical composition matching kaolinite (SiO₂ ~44%, Al₂O₃ ~41%), and Willbourn identified the Bukit Medan clay as the same rock type weathered in place (pp. 11, 25).
Conclusion
Willbourn’s definitive takeaway is that Johore’s mining economy rests almost entirely on the Bukit Medan iron mine, whose output was expanding rapidly and whose geological origin—if the hydrothermal-alteration theory proves correct—may conceal very large underground reserves. Tin, despite the State’s granite geology, offers only marginal and short-lived prospects in shallow alluvial deposits, with the sole exception being the untested high-level alluvium, which warrants systematic deep boring before any firm judgement can be made.
Context
- The fieldwork drew on the Government Geological Survey Department’s records and the 1926 Revenue Survey Map of Johore; Willbourn’s coloured geological map at 3 miles to 1 inch was prepared for the Department but only a black-and-white sketch map was published in the journal (p. 5).
- The article represents the first comprehensive geological account of Johore, filling a gap left by Fulton’s premature departure from the Survey in 1924 due to illness; it is a foundational reference for the State’s geology and mining history.