TEHRAN - Natural bitumen, also known as asphaltite or gilsonite, is a solid hydrocarbon resin found in specific geological formations and is a significant natural resource found in western Iran’s Ilam province.
Situated along the border with Iraq, Ilam, the province with the lowest population in Iran, is one of the country’s main sources for natural bitumen production, alongside Kermanshah and Lorestan.
This resource plays a vital role in the province’s economy, contributing to both domestic use and international exports, particularly for road construction, waterproofing, and industrial applications.
A naturally occurring hydrocarbon resin, natural bitumen is formed from the evaporation of volatile components in crude oil over millions of years.
It appears as glossy, black lumps with high solubility in organic solvents, high purity, high molecular weight, and low ash content (typically 1-10 percent).
Natural bitumen contains 70-80 percent carbon, 3–7 percent sulfur, and 9–18 percent ash, depending on the deposit, and has a softening point between 130–250°C.
In Ilam province, natural bitumen is found in the Zagros Mountains, particularly in the Gachsaran and Asmari formations, which are rich in shale, marl, and limestone.
These formations, dating back to the Middle Eocene (47.8 to 38 million years ago), host bitumen deposits formed through processes like oxidation, polymerization, and reaction with sulfur, where crude oil seeps to the surface, loses volatile components, and hardens into solid bitumen.
Ilam’s natural bitumen deposits are primarily located in the Seymareh, Mehran, and Dehloran regions, with notable sites including the Dehloran Bitumen Spring, a unique natural monument where bitumen flows to the surface alongside hot water.
A unique geological feature located 7 km from Dehloran city, this spring has been active for thousands of years, bringing black bitumen to the surface with hot water (50°C).
The spring’s pond is 9 meters in diameter and 50 cm deep, fenced to protect wildlife. It is Iran’s only bitumen spring, recognized as a national natural monument, and highlights Ilam’s geological significance.
Iran holds approximately 15 million tons of natural bitumen reserves, accounting for 15 percent of the global total (100 million tons), making it the third-largest holder after the United States and Canada (65 percent combined).
Ilam is the second-largest province for natural bitumen reserves in Iran, behind Kermanshah. The country produces over 6 million tons of bitumen annually, including both natural and refined, of which natural bitumen makes up a quarter.
The province’s output supports Iran’s 8percent share of the global bitumen market (125 million tons in 2021). Exact reserve and production figures for Ilam alone are not specified in credible sources, but the province’s contribution is substantial within Iran’s 1.5 million tons of annual production.
Natural bitumen in Ilam is extracted through underground and open-pit mining, targeting vertical veins in the Gachsaran and Asmari formations, with modern excavators used to extract vertical bitumen veins.
The process involves drilling and blasting to access bitumen, which is then crushed, heated, and processed into lumps or micronized powder for various applications.
Traditional methods persist in some areas, leading to inefficiencies and environmental concerns, but modern equipment like excavators is increasingly used.
Key extraction sites include Seymareh, which hosts significant bitumen deposits within the Gachsaran formation, with 76 percent carbon and 5.1 percent sulfur content, as well as Mehran and Dehloran. The latter’s proximity to oil fields like Cheshme Khosh enhances its bitumen production.
After extraction, bitumen is transported to processing plants, where it is broken into lumps, milled into powder, and graded based on ash content and particle size. Local companies in Ilam process gilsonite for export, ensuring low ash content and high purity.
Natural bitumen from Ilam is versatile, with applications across multiple industries due to its waterproofing, adhesive, and durable properties. The primary use, accounting for 85 percent of Iran’s bitumen consumption, is in asphalt for road paving.
Ilam’s natural bitumen, with 70–80 percent carbon content, is crushed, heated, and mixed with aggregates to create durable road surfaces. It is often blended with refined bitumen to enhance hardness and longevity.
Its impermeability to water makes it ideal for roofing, floor insulation, and sealing buildings. Ilam’s bitumen is used in Iran’s construction industry and exported for similar purposes.
Natural bitumen is also used to coat pipelines to prevent corrosion, a critical application given Iran’s oil and gas sector, which incurs 3-5 percent of Gross Domestic Product (GDP) in corrosion-related costs annually. It is also used in drilling cement and as a sealant.
Its high solubility in organic solvents makes it suitable for varnishes, stains, and protective coatings in the paint industry. Natural bitumen further serves as an additive in casting and as a fuel source, similar to coal, due to its high carbon content.
In ancient times, Ilam’s bitumen was used for making cylinder seals, waterproofing buildings and treating diseases. Today, it is also used in adhesives and sealants.
While Ilam’s economy is dominated by agriculture and oil/gas, with $1.169 billion in exports annually (2024 estimate), natural bitumen is a growing contributor.
Iran is the world’s fourth-largest bitumen producer and the regional top exporter, with Ilam contributing significantly to exports to countries like India, China, Turkey, the UAE, and African nations.
Natural bitumen’s competitive pricing and high quality (low ash and high carbon) make it globally sought-after. The global market is projected to reach $143.84 billion by 2030, with Ilam’s output supporting Iran’s competitive position.
Bitumen mining and processing create jobs in Ilam, particularly in Dehloran and Mehran, though the sector is less labor-intensive than agriculture.
In 2019, Ilam’s governor announced a $135 million investment for oil and gas projects, including exploration in Bijar canyon, which may include bitumen prospects. These projects aimed to enhance production capacity.