Brown Diamond

Related: Diamond Varieties

Blue DiamondDiamondPink DiamondYellow Diamond

Key Differentiators

• Most common fancy color — approximately 80% of all diamonds are brown or near-colorless
• Argyle mine grading: Champagne C1–C5, Cognac C6–C7
• Color from plastic deformation (more severe than pink); vacancy clusters contribute
• Extremely HPHT-treatment-susceptible — most colorless HPHT-treated diamonds were originally brown
• Thermal conductivity — passes diamond tester; RI 2.417

Natural vs. Synthetic

Synthetic brown diamond is commercially available (HPHT synthesis (brown is an intermediate or transitional color in HPHT process; deliberate brown synthesis is uncommon as HPHT typically targets colorless or yellow), CVD synthesis (as-grown CVD diamonds are often brown; require post-growth HPHT treatment to achieve colorless)). Distinguishing natural from synthetic typically requires microscopic examination of internal features.

• DiamondView (UV fluorescence imaging): Natural brown diamonds show broad irregular blue or blue-green fluorescence patterns reflecting natural octahedral growth. Graining-related strain visible in pattern. Synthetic: HPHT synthetic shows cuboctahedral sector geometry. As-grown CVD shows columnar layered pattern with orange sectors. CVD brown (pre-HPHT) shows characteristic banded pattern.
• Spectroscopy (FTIR): Natural brown diamonds often show Type Ia nitrogen (B-aggregates, N3 center). Some show 3107cm-1 hydrogen absorption. Nitrogen aggregate pattern reflects geological thermal history. Synthetic: HPHT synthetics typically Type IIa or Type Ib (isolated nitrogen). As-grown CVD diamonds often show nitrogen-related bands inconsistent with natural geological aggregation. Si-V at 737nm (CVD).
• Loupe — graining and inclusions: Brown graining lines (parallel deformation planes) visible under magnification. No metallic inclusions. Synthetic: HPHT: metallic flux inclusions (Fe/Ni/Co), magnetically attracted. CVD: columnar growth patterns, graphite inclusions in planar arrangement. No graining planes from natural plastic deformation.

Common Simulants

• Smoky Quartz: DR (uniaxial positive); RI 1.544–1.553; SG 2.65; hardness 7; much lower RI and SG; fails diamond thermal tester; conchoidal fracture visible.
• Brown Topaz: DR (biaxial positive); RI 1.629–1.637; SG 3.53; hardness 8; perfect basal cleavage {001}; fails diamond thermal tester.
• Brown Zircon: DR (uniaxial positive); RI 1.925–1.984 (high type); SG 4.69; hardness 7.5; strong facet doubling visible under loupe; fails diamond thermal tester.
• Hessonite Garnet: SR but RI 1.742–1.748; SG 3.65; hardness 6.5–7.5; heat shimmer inclusions (treacly texture); fails diamond thermal tester.
• Chocolate Tourmaline (Brown Dravite): DR (uniaxial negative); RI 1.624–1.644; SG 3.06; strong pleochroism; hardness 7–7.5; fails diamond thermal tester.
• Brown Cubic Zirconia: SR; RI ~2.15 (lower than diamond); SG 5.60–5.90 (much heavier); hardness 8–8.5; fails diamond thermal tester.

Treatments

• HPHT Treatment (decolorization or color change)
• Irradiation (+ annealing)
• Surface Coating

Price Context

Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.

About Brown Diamond

Brown diamonds are the most abundant fancy color. Brown color arises from plastic deformation creating vacancy clusters and graining planes. HPHT treatment routinely converts brown diamonds to near-colorless or other fancy colors. The Argyle mine used an internal scale of Champagne (C1–C5) and Cognac (C6–C7) to grade this material.