Diamonds from the Nassau Mountains, Suriname

Expanded Overview of Diamonds in Suriname

Geological Context

The diamonds found in Suriname are part of the Marowijne greenstone belt, a segment of the broader Guiana Shield, which stretches across northern South America (Venezuela, Guyana, Suriname, French Guiana, and Brazil). This belt is part of a 1,500-km-long granite-greenstone terrane that formed during the Transamazonian orogeny (~2.18–1.95 billion years ago), a major tectonic event resulting from the collision of the Amazonian and West African cratons.

Diamond Occurrence and Mining

• Discovery & History: Diamonds were first discovered in Suriname in the late 19th century, primarily in alluvial deposits along rivers and creeks.
• Primary Source: The Paramaka Creek area in the Nassau Mountains (a horseshoe-shaped range in northeastern Suriname) is the most significant known diamond-bearing region.
• Mining Methods: Most extraction has been through artisanal and small-scale mining (ASM), with workers panning and dredging river sediments. No major kimberlite or lamproite pipes (primary diamond sources) have been economically exploited yet.

Diamond Characteristics

1. Type & Composition:

• Predominantly Type IaAB diamonds, meaning they contain nitrogen aggregates (A and B centers).
• Indicates prolonged geological storage in the mantle before being brought to the surface.

1. Color & Appearance:

• Common colors: Colorless, brown, and slightly greenish.
• Some stones exhibit green or brown irradiation spots, likely due to natural radiation exposure during transport.
• Surface features: Evidence of resorption (partial dissolution) during their ascent to the surface, suggesting interaction with deep mantle fluids.

1. Mineral Inclusions:

• Forsterite (Mg-rich olivine) and enstatite (Mg-rich pyroxene) inclusions indicate a peridotitic paragenesis, meaning the diamonds formed in mantle peridotite at depths of 150–250 km.
• These inclusions help trace the diamonds’ origin to the lithospheric mantle beneath the Guiana Shield.

1. Growth & Luminescence:

• Concentric growth patterns suggest formation in multiple growth stages within the mantle.
• Blue and/or green luminescence under UV light, possibly due to nitrogen defects or other impurities.

Geodynamic Implications

The diamonds were transported to the surface via kimberlite-like volcanic eruptions (though no major pipes have been confirmed in Suriname yet). Their presence in alluvial deposits suggests:

• Erosion of primary sources (possibly hidden kimberlites).
• Long-distance fluvial transport from upstream deposits in the Guiana Shield.

Economic & Exploration Potential

• Suriname’s diamonds are generally small (mostly under 1 carat), limiting large-scale commercial viability.
• However, the Marowijne greenstone belt remains underexplored, and further discoveries of primary deposits (kimberlites/lamproites) could enhance economic prospects.
• Similar geology to Guyana’s diamond fields (e.g., Kurupung district) suggests potential for more finds.

Conclusion

Suriname’s diamonds provide valuable insights into the deep mantle processes of the Guiana Shield. While current production is artisanal, the region’s geological setting parallels other diamond-rich areas in South America and West Africa (before continental drift), hinting at untapped potential for future discoveries.

Would you like additional details on specific mining areas or comparisons with neighboring Guyana’s diamond fields?

Diamonds in Guyana: Geology, Mining, and Economic Significance

Guyana, like neighboring Suriname, is part of the Guiana Shield, a Precambrian geological formation rich in mineral resources, including gold and diamonds. Guyana’s diamond deposits have been mined for over a century, primarily from alluvial sources, with increasing interest in potential primary (kimberlite) sources.

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1. Geological Setting

A. Diamond-Bearing Regions

Guyana’s diamonds are mainly found in:

• Mazaruni River Basin (notably the Kurupung district) – The most productive area.
• Cuyuni River Basin
• Potaro River Basin (near the famous Kaieteur Falls)
• Rupununi Savannah (less explored but shows potential)

B. Host Rocks & Source

• Alluvial Deposits: Most diamonds are recovered from river gravels, indicating erosion of primary sources.
• Kimberlite Potential: Unlike Suriname, Guyana has confirmed kimberlite pipes, including:
• Kurupung Kimberlite Field (Mazaruni) – The most studied area, with multiple pipes.
• Arakaka Kimberlites (northwestern Guyana) – Less explored but diamondiferous.
• Toroparu Kimberlite (associated with gold deposits).

These kimberlites are part of the Guiana Craton, which shares geological similarities with West Africa (before continental drift), suggesting a connection to ancient diamond-forming events.

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2. Diamond Characteristics

A. Types & Quality

• Predominantly Type IaAB (like Suriname’s diamonds), with nitrogen aggregates.
• Colors: Mostly colorless, brown, and yellowish, with rare pink and blue stones reported.
• Size Distribution: Generally small (0.1–0.5 carats), but occasional large diamonds (e.g., a 33-carat stone found in 2019).

B. Mineral Inclusions

• Peridotitic Suite: Olivine (forsterite), enstatite, and chromite inclusions, suggesting formation in the lithospheric mantle (150–250 km depth).
• Eclogitic Inclusions (rare): Indicate some diamonds formed in subducted oceanic crust.

C. Surface Features & Morphology

• Resorption textures (rounded edges) due to mantle-derived magma transport.
• Octahedral and dodecahedral forms common, with some alluvial abrasion.

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3. Mining & Production

A. Historical Context

• Diamonds were first discovered in the late 19th century alongside gold.
• 1930s–1960s: Peak production under British colonial rule.
• Post-independence (1966): Decline due to lack of investment, but artisanal mining continued.

B. Current Mining Methods

• Artisanal & Small-Scale Mining (ASM):
• Manual panning in rivers.
• Dredging operations in alluvial deposits.
• Formal Exploration:
• Companies like Guyana Goldfields (now Reunion Gold) and Troy Resources have explored kimberlites.
• Toroparu Project (Gold X Mining) has diamond potential alongside gold.

C. Production & Economy

• Annual Production: ~50,000–100,000 carats (unofficial estimates may be higher).
• Export Markets: Mostly sold through Antwerp and Dubai.
• Challenges:
• Lack of large-scale industrial mining.
• Smuggling to neighboring countries (Venezuela, Brazil).
• Environmental concerns (mercury use in alluvial mining).

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4. Comparison with Suriname’s Diamonds

Feature	Guyana	Suriname
Primary Sources	Confirmed kimberlites (Kurupung)	No major kimberlites confirmed (alluvial only)
Diamond Colors	Colorless, brown, yellow, rare pinks/blues	Colorless, brown, greenish
Mining Scale	Larger ASM sector, some corporate interest	Mostly artisanal, less formal exploration
Geological Age	Transamazonian Orogeny (~2.0 Ga)	Similar (Marowijne Belt ~2.18–1.95 Ga)

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5. Future Prospects

• Kimberlite Exploration: Guyana has better potential for discovering economic primary deposits than Suriname.
• Formalization of ASM: Government initiatives to regulate and support small miners could boost production.
• Industrial Potential: If large kimberlite deposits are confirmed, Guyana could attract major diamond miners like De Beers or Rio Tinto.

Conclusion

Guyana’s diamonds, though smaller on average than those from major producers, have significant geological and economic potential. The confirmed presence of kimberlites makes Guyana a more promising candidate for future large-scale diamond mining compared to Suriname. Increased investment in exploration and formalization of artisanal mining could unlock greater value from this sector.

Would you like details on specific mining projects or comparisons with other Guiana Shield countries