Diamond prices in August 2026: natural slips, lab-grown falls harder

The August 2026 Caratlytics Diamond Price Index puts natural diamonds at a median of $2,184.28 USD per carat, down 4.89% from July, and lab-grown at $464.15 per carat, down 12.2%. The natural to lab ratio has widened to 4.7 to 1, up from 4.3 to 1 last month, with natural carrying a 370.6% premium. Both segments fell; the gap between them grew.

Segment	Median (USD/ct)	Prior month	Month on month	Listings
Natural	2,184.28	2,296.54	-4.89%	735,076
Lab-grown	464.15	528.66	-12.20%	1,424,754
Overall	793.65	899.56	-11.77%	2,159,855

Shape by shape, August hurt

The natural side produced two genuine moves this month. Asscher naturals gained 11.1%, the largest movement in either direction across natural shapes, reaching $2,601.46 per carat. Radiant rose 6.0% to $2,764.93 per carat. Both are specialty cuts with lower listing volumes where monthly swings can be sharper, and neither gain reflects a broad market recovery. Cushion natural also eked out a small gain, up 1.1% to $2,791.67 per carat.

The falls are more instructive because they hit the most popular shapes. Oval naturals dropped 9.6% to $2,379.78 per carat. Pear fell 9.0% and Marquise fell 8.8%. Round natural, which functions as the market anchor, slipped a more contained 3.8% to $2,094.31 per carat. Emerald fell 6.6% and Princess came off 3.2%. These aren't corrections in niche cuts; they're broad across the shapes that actually move volume.

Lab-grown had a harder month almost everywhere. Cushion and Marquise both fell 14.7%. Round fell 14.1% to $437.50 per carat. Radiant dropped 12.5%. Asscher was the only lab shape in positive territory, up 3.3% to $525.88 per carat. Even that gain was slight, and irrelevant to most buyers shopping the shapes that account for real volume.

Shape	Natural (USD/ct)	Natural MoM	Lab-grown (USD/ct)	Lab MoM
Round	2,094.31	-3.8%	437.50	-14.1%
Oval	2,379.78	-9.6%	487.01	-11.2%
Cushion	2,791.67	+1.1%	465.92	-14.7%
Princess	2,073.10	-3.2%	481.28	-7.3%
Emerald	2,166.20	-6.6%	493.87	-6.7%
Pear	2,102.68	-9.0%	478.10	-9.3%
Marquise	2,113.89	-8.8%	500.00	-14.7%
Radiant	2,764.93	+6.0%	473.11	-12.5%
Asscher	2,601.46	+11.1%	525.88	+3.3%
Heart	2,261.27	+1.7%	439.50	-9.4%

The certification gap

Which certificate comes with a stone isn't a formality. It places you in a different price tier, and the August data makes the scale of that difference concrete.

For natural diamonds, IGI-certified stones sit at a median of $1,632.94 per carat against GIA's $2,241.94. HRD natural comes in at $2,638.63 and EGL at $2,701.51. The EGL figure deserves scrutiny: EGL has historically applied looser grading standards than GIA, which means a stone graded EGL at $2,701 per carat may not represent the same actual quality as a GIA stone at a lower number. Buyers comparing across cert labs should factor this in.

For lab-grown, the spread is considerable. GIA-certified lab-grown stones sit at $1,141.54 per carat, while IGI sits at $445.75. GCAL comes in at $1,059.27. GIA certifies relatively few lab-grown diamonds, and its sample skews toward premium goods. A GIA lab-grown listing and an IGI lab-grown listing at similar carat weights are not comparable at face value.

Cert lab	Natural (USD/ct)	Lab-grown (USD/ct)
GIA	2,241.94	1,141.54
IGI	1,632.94	445.75
HRD	2,638.63	n/a
GCAL	n/a	1,059.27
EGL	2,701.51	n/a

Where retailers diverge

The cross-retailer spread data is one of the more consequential outputs our index produces. In August, 4,645,741 certified diamonds were listed simultaneously at more than one of the 127 active retailers in the index, out of 13,999,549 certified diamonds tracked overall.

For natural diamonds, the median spread for the same stone across retailers is 39.7%, with an average of 55.5%. The same certificate number, the same graded stone, priced nearly 40% apart at the midpoint of the distribution. The aggregate value of that pricing gap across all natural stones listed at more than one retailer is $3,081,649,647.

Lab-grown spreads are wider still. The median is 118.5% and the average 138.9%. The aggregate spread value for lab-grown stones listed at more than one retailer is $2,286,908,565. The absolute dollar amounts are smaller than for natural diamonds because lab-grown prices are lower, but the proportional inconsistency across retailers is extraordinary. A buyer who takes the first lab-grown listing they see, without checking whether the same stone is listed elsewhere at a lower price, is paying a premium that has nothing to do with quality.

Checking where a specific certified stone appears across retailers is, at these spread levels, the most productive thing a buyer can do before committing.

What August means for buyers right now

For natural diamond buyers, the Oval, Pear, and Marquise drops create a genuine opportunity. Oval natural at $2,379.78 per carat, down 9.6% from July, is meaningfully more accessible than it was a month ago. The 1 carat natural pricing data gives useful context on how that shift lands across different size points. A stone that was out of budget in July may be in range now, particularly in the oval.

The Asscher and Radiant natural gains don't automatically mean paying a premium is justified. Both shapes trade in thin markets, and August's moves may reflect a handful of premium stones rotating through the sample rather than a broad price shift. The interquartile range for all natural diamonds runs from $1,543.03 to $3,588.24 per carat. Where a specific stone sits in that spread matters more than the shape's headline movement.

For lab-grown buyers, the falls across the board look like a buyer's window, though the floor isn't yet visible. Emerald lab-grown fell 6.7% and Princess fell 7.3%, while Cushion and Marquise fell more than twice those figures. If value stability over time matters, Emerald and Princess held relative ground this month. Shapes that fell 14.7% can fall further.

The natural versus lab-grown comparison looks different today than it did six months ago. The natural premium is 370.6% and the ratio is 4.7 to 1. That ratio widened in August because lab-grown dropped faster, not because natural became more expensive.

What to watch in September

Three things matter in the next release.

Whether the Asscher and Radiant natural gains hold. Both moved in low-volume markets. A reversal next month would confirm August was statistical noise rather than trend.

Whether lab-grown finds any floor. Cushion and Marquise fell 14.7% in a single month from a market with 1,424,754 active listings. Supply continues to outrun demand, and nothing in August's data signals a reversal. Buyers who can wait may continue to benefit; buyers who need to purchase now should anchor their price expectations to August's numbers rather than July's.

And whether the cross-retailer spread on lab-grown begins to compress. At a median of 118.5%, the lab-grown market has not reached price consensus across retailers. When that spread narrows, it tends to indicate a market settling on what things are worth. It hasn't yet.

The September release lands in October. The natural median to hold against it: $2,184.28 per carat.