Heritage Auctions’ September 29 Fall Fine Jewelry Signature® Sale is still a few weeks away, but four loose gems and a mounted diamond are already calling us to stop and look, and we thought you might want to get a closer look too; a 3.15-carat Brazilian Paraiba tourmaline with spectacular color, a 2.46-carat no-heat Burmese ruby, an obvious 2.35-carat Kashmir sapphire, and a rare 10.96-carat Zimbabwe (Sandawana) emerald.
The ruby and sapphire are begging for some repolishing, as they look like they have great improvable potential.
And just for a little ice-ing on the cake, we highlight a nice piece of ice – a 10.13-carat Old Mine (Cushion? “Roval”?) Brilliant cut diamond set in platinum. You make the call on the shape… [We’ll talk… gr]
Brazilian Paraiba Tourmaline
Images Courtesy of Heritage Auctions
3.15 ct Brazilian Paraiba Tourmaline
Shape: Cushion
Measurements: 8.79 x 7.74 x 6.58 mm
Treatment: Insignificant to Minor clarity enhancement
Origin: Brazil
Report: AGL #1147352
Property from a Colorado Collector
Estimate: $50,000 – $70,000.
Condition Notes:
Heritage notes that this particular unmounted deep blue Paraíba tourmaline from the copper-rich elbaite deposits of Brazil (where the first gems of this rare color were first discovered), is accompanied by an AGL, American Gemological Laboratories’ Prestige Gemstone Report, dated May 6, 2025.
True Brazilian Paraíba tourmalines (as opposed to Nigerian and Mozambican copper-bearing tourmalines, also referred to as “paraiba” tourmalines) are recognized for their vivid saturated color and rarity. This stone shows strong saturation, in a deep blue hue—sometimes noted as “Heitorita” (see our feature Brazilian Paraíba Tourmaline: Vivid Blue “Heitorita” Color)—that “is commonly the result of a relatively low-temperature heating process”—an accepted practice for this gem type. The AGL report records only insignificant to minor clarity enhancement has been detected. Minute chips are present around the crown facets under magnification but are not readily visible without it.
Kashmir Sapphire
Images Courtesy of Heritage Auctions
2.35 ct Kashmir Sapphire
Shape: Modified octagonal
Measurements: 6.97 x 6.02 x 5.59 mm
Treatment: No gemological evidence of heat
Report: AGL # 1108814; Gubelin # 25062175
Estimate: $30,000 – $40,000.
Condition Report:
This gem is accompanied by two gemological reports; one from the Gübelin Gem Lab and another from the American Gemological Laboratories. Both labs reported that the gem comes from Kashmir, and that there is no evidence of heat.
Heritage notes that “Kashmir sapphires are among the most coveted gemstones in the world, renowned for their legendary cornflower blue hue, velvety texture, and origins in the remote, politically sensitive areas of the Himalayas. Mined primarily between 1881 and 1887 in the high-altitude Zanskar range following a mountain landslide, the original deposit was swiftly depleted, cementing their reputation for extraordinary rarity.”
“Possessing an older cutting style, the stone shows moderate abrasions to the large culet, that slightly extend onto the pavilion mains.”
“Older Cutting Style”
Before we talk old cutting styles, just look at that color! True – we are looking at a picture. But you can definitely see that velvety Kashmir blue appearance, and that’s difficult to capture in an image.
Okay – now let’s talk cutting style. One discerning look at the gem reveals misshapen facets and an off-center culet—visible through the crown, the culet sits noticeably off to one side. The profile diagram of the gem on the AGL report confirms this (see above). The trade would refer to this disregard for symmetry and proportions as “native cut” where facet shape and proper proportions take a back seat to weight and color retention.
Sandawana Emerald
10.96 ct Emerald
Shape: Octagonal
Measurements: 17.19 x 12.92 x 6.41 mm
Treatment: Clarity enhanced (F1)
Origin: Zimbabwe (Sandawana)
Report: GIA # 2235646043
Estimate: $20,000 – $30,000.
Condition Report:
Accompanied by a GIA report, this emerald has been identified as having come from the Sandawana mining district in Zimbabwe.
Sandawana:
Emerald Mining in Zimbabwe has disappeared commercially. It is said that at its peak in the 1970s and early 1980s, Sandawana had become world-famous for producing small but exceptionally vivid green emeralds with high chromium content. Maybe one of the most consistent producers of fine-quality emeralds anywhere, Sandawana reportedly exceeded 100,000 carats a year.
Today, Sandawana has emerged as a significant lithium mining region. Estimates place Sandawana at tens of millions to 100 million tons of lithium ore – not that this is gemologically important, but we thought you should know.
Back to our Rare Emerald
Heritage did it’s history research as well. “This 10.96 carat emerald originates from the famed Sandawana mines in Zimbabwe’s Mweza Greenstone Belt, a region known for producing some of the world’s most vividly colored emeralds. Discovered in the late 1920s and commercially mined by the 1950s, Sandawana gained a reputation for high-quality emeralds, particularly melee. Most stones from this locality are small, making this gem exceptionally rare and desirable among collectors. The mine’s remote location and artisanal mining practices have always limited production, with current activity remaining sporadic. Large fine stones like this are rarely seen, with a clean surface and minor cavities on the pavilion where inclusions reached the surface during cutting. Inclusions are moderate to the naked eye and consistent with F1 clarity enhancement.”
Burma Ruby
2.46 ct Burma Ruby
Shape: Oval
Measurements: 8.28 x 6.13 x 4.64 mm
Treatment: No indications of heating
Report: GIA # 2201298090
Estimate: $20,000 – $30,000.
Overall Condition Report
Heritage notes that “Burmese rubies are primarily mined in the Mogok Valley of northern Myanmar (formerly Burma), a region renowned for centuries as one of the world’s most prestigious sources of rubies.” As we just reported last week, Mogok is in the middle of a civil war. (see Mogok Under Attack here.)
“Praised for their vivid color and exceptional clarity, these gems have long set the global standard for ruby quality. This particular specimen is an outstanding example of Burmese material and would make a great centerpiece for a ring or pendant. Two minor cavities and a surface reaching feather define the pavilion side under magnification.”
Some repolishing could make a significant difference in beauty and salability.
Old Mine Cut Diamond
Details, details…
On the GIA report (seen below), this diamond is described as an Old Mine Brilliant. Heritage Auctions calls it an Old Mine Cut. So what’s the difference?
The older term, Old Mine Cut, has apparently been causing some confusion (although we are not 100% sure that the diamond trade is confused). These days, “cut” refers to proportions & finish (polish and symmetry). But in this case, Old Mine Cut was meant to describe what we now call shape and cutting style—a squarish, chunky brilliant-cut diamond with a small table and an obvious culet – and nothing regarding symmetry or polish.
That’s why, in the GIA report below, the description reads Old Mine Brilliant. For practical purposes, let’s just say that Old Mine Cut and Old Mine Brilliant are the same thing.
Definition of an Old Mine Diamond / Old Mine Brilliant
We’ve always been told that an Old Mine diamond—whether you call it an Old Mine Cut or Old Mine Brilliant—was fashioned to follow the natural shape of the typical rough crystal, the octahedron.
Before the diamond saw, cutters couldn’t polish two diamonds from the same rough octahedron. They could only cut one stone, trying to save as much weight as possible. This meant that the pavilion ended up deeper than today’s modern brilliants, and the crown higher and steeper. To preserve weight, cutters polished off only what they felt was absolutely necessary from the top octahedral point, leaving a small table.
The culet was another story. The thinking at the time was that the bottom point of the diamond needed protection. To prevent cleaving from the culet up the pavilion side of the stone, cutters polished a sizable facet on the bottom—hence we ended up with a large culet on Old Mine diamonds.
OMC Shape
The outline of an Old Mine Cut mirrors the outline of the octahedral crystal—squarish, with slightly rounded corners. Today we’d call that a cushion shape.
So… what’s the shape of this “Old Mine Brilliant”?
Look closely at the outline: on two “longer” sides, the edges are fairly flat; on the shorter sides, they’re more curved/rounded. Two corners look squarish, the other two more curved/rounded.
And this is where we are simply going to have to stop trying to force a somewhat squarish diamond into a somewhat round-ish category. This 10-carat diamond is an old cut—an Old Mine Cut—not round enough to be called an Old European Cut, and not modern enough to be called a Cushion Brilliant. [We thought about calling it an Old Mine “Roval” – a round-oval. – What do you think?]
Diamond, Platinum Ring
Stones: Mine-cut diamond weighing 10.13 carats;
baguette-cut diamonds weighing a total of
approximately 0.45 carat
Metal: Platinum
Gross Weight: 6.10 grams
This diamond is accompanied by a GIA Report # 2235471507, dated December 30, 2024, stating F color, SI2 clarity
Estimate: $150,000 – $200,000.
Condition Report
Pleas read this description from Heritage… “A beacon of a ring, anchored by a bold old mine-cut diamond; chunky, brilliant, and full of soul. Its broad facets catch the light flickering with antique romance.” Here we have a 10-carat Old Mine Cut brilliant. It’s big, it has the classic small table and slightly large culet, a tall crown and deep pavilion. These diamonds were shaped not only to save weight from the rough, but to perform under candle light.
