Cutting Zultanite costs about 97% of the rough crystal’s weight, according to the trademark holder Zultanite Gems LLC. The reason is mineralogical: gem-quality diaspore has perfect cleavage on the {010} plane, so the cutter must orient the table to the optic axis to preserve the color-change effect — a constraint that conflicts with maximum-yield orientation. The polished gem typically weighs about three percent of the original rough.

What “97% loss” actually means

The figure is repeated in nearly every commercial description of Zultanite, and like most repeated figures it deserves a careful read. Zultanite Gems LLC describes the lapidary process as producing “approximately 97% crystal loss” during cutting, with the polished stone weighing “only about 3% of the original rough.” The figure is a manufacturer claim — not a peer-reviewed measurement — but it is consistent with what perfect-cleavage gems require when cut for orientation than yield.

For context: a typical faceted sapphire retains 25 to 35 percent of the rough by weight; a typical faceted emerald retains 30 to 50 percent depending on quality and inclusion structure; a routine diamond cut retains around 50 percent for round brilliants. A 97 percent loss puts color-change diaspore at the extreme end of the lapidary-difficulty spectrum, comparable to the highest-yield-loss work in alexandrite or in fragile color-change garnets.

The practical translation: a faceted Zultanite of five carats represents, by these figures, an original rough crystal weighing approximately 165 carats. Stones above five carats finished are described by the trademark holder as “exceptionally rare,” which the arithmetic here helps explain.

The mineralogy that drives the loss

Two physical properties of gem-quality diaspore force the high-loss cutting style.

Perfect cleavage on the {010} plane. Cleavage is the tendency of a crystal to split along specific planes of weakness in its atomic structure. “Perfect” in mineralogical usage means the cleavage is so clean that fracture surfaces are smooth and reflective, and the plane of weakness can be exploited deliberately. Diaspore’s {010} cleavage is one of the most expressed perfect cleavages in gem mineralogy. A blow struck along that plane — or an inadvertent blow during faceting — can split the stone cleanly, sacrificing the entire piece.

The cleavage is not an inclusion defect; it is structural. It exists in every diaspore crystal because it is built into the orthorhombic symmetry of the species. The cutter cannot avoid it; the cutter can only work around it.

Optic-axis orientation requirement for color change. The alexandrite effect in Zultanite depends on the path length the light travels through the crystal along a specific axis. To extract maximum color-change strength, the cutter aligns the table — the largest flat facet on top of the stone — perpendicular to the optic axis along which the absorption profile produces the strongest spectral contrast. This orientation does not coincide, in many crystals, with the longest dimension of the rough. The cutter must therefore choose between cutting for color or cutting for size. Cutting for color sacrifices weight.

The two constraints compound. The cleavage plane forces conservative cutting angles to avoid splitting; the optic-axis requirement forces a specific orientation that may waste large volumes of the rough; and the gem’s intermediate hardness (6.5 to 7 on the Mohs scale) means it polishes more slowly than corundum or beryl, demanding patience and increasing the risk that a long polishing pass will encounter and propagate a hidden cleavage flaw.

How a Zultanite is cut

The procedure followed by master cutters working with gem-quality diaspore generally proceeds in five stages, each of which can sacrifice further weight from the rough.

1. Crystal evaluation. The rough crystal is examined under polarized light to identify the optic axis and the cleavage planes. The cutter maps the crystal’s internal structure and inclusions before any cut is made.
2. Initial sawing. The crystal is sawn — never cleaved deliberately — into a preform that respects the optic axis and avoids the cleavage planes wherever possible. This is the largest single weight loss in the process: the saw kerf is thin, but the geometric requirement of orienting the preform correctly often means cutting away substantial portions of the rough.
3. Pre-forming. The preform is shaped on a coarse grinding wheel into the rough outline of the final cut — typically an oval, cushion, or marquise to accommodate the often-elongated rough. Octagons and rounds are less common because they fit poorly to the rough crystal habit.
4. Faceting. The pavilion (lower portion) and crown (upper portion) facets are cut on a faceting machine using diamond-charged laps. Each facet is set at angles calculated to optimize light return through the table while respecting the optic-axis orientation. The cutter monitors the color change at each stage; a facet placed at the wrong angle can dampen the effect.
5. Polishing. The final polish brings the facets to optical clarity. This stage is where hidden cleavage flaws are most likely to propagate; a polish pass that catches a {010} plane can split the stone and sacrifice the entire investment of the previous stages.

The cumulative loss across these stages is what produces the famous 97 percent figure. The largest single loss is usually the initial sawing for orientation. The most catastrophic loss is a cleavage failure during polishing — relatively rare in skilled hands, devastating when it occurs.

Why the cutting concentrates in expert hands

The technical demands of cutting color-change diaspore filter the supply of finished stones through a small population of master cutters who have developed specific expertise in the species. The trademark holder works with selected cutters; the same is true of other firms producing material under the Csarite, Ottomanite, and Turkizite trade names.

The skill set required is not interchangeable with diamond cutting or even with general colored-stone cutting. A cutter accustomed to cutting sapphires for maximum yield will lose more material on a Zultanite rough than a cutter who has learned the diaspore-specific orientation rules. The learning curve is real, the failure cost is high, and the volume of available rough is low — which means the population of cutters with verifiable Zultanite experience remains small.

For a buyer, this concentrates importance on provenance. A Zultanite cut by a known specialist, with a lab report identifying the species and grading the color change, is a substantially different proposition from an uncertified stone of unverified origin. The uncertified stone may be perfectly genuine; it may also be a different gem species sold under the wrong name. Lab reports from the Gemological Institute of America, the American Gemological Laboratories, or comparable institutions are the standard verification.

What the 97% figure does not mean

Three common misreadings of the lapidary loss figure deserve correction.

It does not mean Zultanite is the highest-loss gem in the world. Several gem species have comparable or worse yields under specific cutting conditions. Tanzanite, for example, also has perfect cleavage and is routinely cut at high loss when the rough is small or oddly oriented. The 97 percent figure makes Zultanite difficult to cut, not uniquely difficult.

It does not mean a 100-carat rough always becomes a 3-carat finished stone. The figure is an average over a wide range of rough sizes and qualities. A particularly clean, well-oriented crystal may yield 5 percent or even 7 percent. A crystal with internal flaws or unfavorable cleavage geometry may yield less than 1 percent. The 3 percent figure is the central tendency; individual stones vary substantially.

It does not justify any specific retail price. Lapidary difficulty is one of many factors in gem pricing. Color-change strength, clarity, size, certification, market demand, and brand attribution all weigh independently. A high-loss-cutting stone may still command a modest price if the color change is weak or the crystal is included; a high-yield stone may command a premium if the color change is exceptionally strong. The 97 percent figure is part of the cost structure, not a price floor.

Implications for buyers and writers

For buyers, the lapidary difficulty has three practical consequences. First, finished Zultanites carry a built-in cost basis higher than gems of comparable raw value but easier cutting; the cutter’s labor and the discarded rough both end up in the price. Second, large finished stones (above three carats) are genuinely scarce, and prices scale steeply with size for that reason. Third, certification matters more for diaspore than for many other species, because the cleavage-related cutting style produces stones with cut-quality variations that lab reports help quantify.

For writers, the 97 percent figure is a manufacturer claim that should be cited as such. It is consistent with the mineralogy and consistent with peer-reviewed accounts of perfect-cleavage gem cutting in general, but it has not been measured in a published study with statistical rigor. Editorial copy should attribute the figure to Zultanite Gems LLC on first use, then can refer to it generically thereafter — “the high lapidary loss characteristic of gem diaspore” — without re-attribution. What editorial copy should not do is round it up to “almost all of the crystal” or down to “most of the crystal,” both of which obscure the specificity of the original claim.

Sources

• Zultanite Gems LLC. “Color-Change Gemstone: Zultanite.” https://www.zultanite.org/color-change-gemstone-zultanite/ — 97% lapidary loss figure, “exceptionally rare” thresholds for stones above five carats. Cited with attribution.
• Wikipedia. “Diaspore.” https://en.wikipedia.org/wiki/Diaspore — perfect {010} cleavage description, hardness range, optical character.
• International Gem Society. “Diaspore Jewelry and Gemstone Information.” https://www.gemsociety.org/article/diaspore-jewelry-and-gemstone-information/ — cleavage, fracture, jewelry suitability notes.
• Klein, C., & Hurlbut, C. S. (1985). Manual of Mineralogy. Standard reference on orthorhombic-system cleavage behavior.
• Hatipoğlu, M., Babalık, H., & Chamberlain, S. C. (2010). “Gemstone potential of the diaspore from the Pinarcik area, Mugla Province, Turkey.” Peer-reviewed locality and gem-quality formation conditions.

Last fact-checked: 2026-04-27.