What kunzite actually is
Kunzite is the pink-to-lilac variety of spodumene, a lithium aluminum pyroxene with the formula LiAlSi₂O₆[IMA][GIA]. The species crystallizes in the monoclinic system with a prismatic-elongate habit and is named for George F. Kunz, the Tiffany & Co. chief gemologist who first identified the variety from a Pala District, California find in 1902, one of the few major gem species with a documented modern discovery and a name traceable to an individual gemologist[AGTA][Gem-A]. Sister varieties of spodumene include green hiddenite (chromium-driven) and colorless triphane.
The optical fingerprints labs use to identify kunzite are refractive index 1.660–1.681, specific gravity 3.15–3.21, birefringence 0.014–0.027, dispersion 0.017, biaxial positive optic sign, and a vitreous luster[IGS][GIA]. Two diagnostic features dominate the species' working character: strong pleochroism (colorless / pink / violet along the three crystallographic axes) and perfect cleavage in two prismatic directions parallel to the c-axis[Gem-A][Gübelin]. The combined constraint, the cut must align the c-axis to the table to display the priced pink face-up, while two cleavage planes meeting parallel to that same axis make the rough split-prone under faceting pressure, makes kunzite notoriously demanding to cut. Well-oriented large clean stones are technical achievements that command premium for cutting alone[IGS].
Color chemistry
Kunzite's pink-to-lilac coloration is driven by trace manganese in the lithium aluminum silicate lattice[GIA][IGS]. The chromophore landscape is single-element-simple compared to most colored gems. Mn³⁺ in octahedral coordination produces the broad absorption that yields the pink-violet hue, and concentration variation across deposits drives the species' three commercial color tiers (Light Pink, Deep Pink, Lilac)[SSEF]. The deeper saturated Deep Pink tier carries the species' apex value premium. The Lilac variant typically shows the strongest pleochroism and is the historic trade signature[GRS].
The strong pleochroism interacts directly with color delivery. Because the pink axis sits along one crystallographic direction and the colorless / violet axes along the others, the cutter's orientation choice fixes the apparent saturation of the finished stone. A mis-oriented cut from saturated rough yields a pale or grayish face-up, while a c-axis-aligned cut from modest rough can deliver a stone that visibly outperforms its raw color grade[Gem-A][Gübelin]. The trade convention is to favor "long" cushions and rectangular step-cuts that maximize the pink axis at the table.
Origin science
Kunzite forms in late-stage granitic pegmatite environments, lithium-rich volatile-saturated melts that crystallize spodumene as the principal lithium ore mineral, with the rare Mn-bearing manganiferous pockets producing gem-grade pink-lilac crystals[USGS][Lotus]. The pegmatite-hosted habit produces the species' characteristic blade-like crystal form, and large clean crystals at 100+ ct are routinely recovered, making kunzite one of the few gem species where decacarat-scale material at modest pricing is the commercial norm rather than the exception[Gem-A].
Three origins anchor commercial supply: Afghanistan (Kunar and Nuristan provinces produce the dominant rough source for saturated lilac and deep pink material. The Kunar belt is the modern apex), Brazil (Minas Gerais is the historic large-crystal source supporting the species' "long" cushion and rectangular cuts), and Madagascar (good-color rough at smaller sizes for mid-tier commercial supply)[IGS][SSEF]. California's San Diego County (Pala District) is the heritage source where Kunz's 1902 type material was identified. Modern California production is collector-grade[AGTA].
Treatment landscape: irradiation, heat, and photolytic fade
Kunzite commerce is dominated by the irradiation-and-heat treatment chain[GIA][LMHC]. Pale-to-near-colorless natural rough is exposed to gamma-ray or electron-beam irradiation, which produces or intensifies the pink-purple coloration via creation of color centers in the crystal lattice. Mild heat may follow to stabilize or modify the resulting hue[Lotus]. Commerce carries this as a single combined Heated / Irradiated state. There is effectively no untreated tier, reflecting that the trade overwhelmingly transacts treated material[CIBJO].
Irradiation of pink rough can also produce a green spodumene material (often marketed as "irradiated green spodumene" rather than as hiddenite, which by gemological convention requires chromium-driven natural color)[GIA][Gem-A]. Detection of irradiation in finished stones is challenging. The treatment is undetectable by standard gemological instruments and requires specialist lab analysis (radiometric residue dating, defect-spectroscopy comparison) at SSEF / Gübelin-tier laboratories[SSEF][Gübelin].
The treatment's defining gemological caveat is photolytic color fade. The irradiated color centers are metastable: prolonged sunlight or strong UV exposure photochemically reverses the color centers and shifts the stone back toward colorless[GIA][IGS]. Natural-color (non-irradiated) kunzite also fades under sustained light exposure, but irradiated material typically fades faster. This makes kunzite the rare gem species where storage discipline (dim conditions when not worn) is a primary care recommendation rather than an optional precaution. Many gemological references warn explicitly[Gem-A][SSEF].
Phenomena science
Cat's-eye kunzite is the species' single documented phenomenon, a chatoyancy variant produced by reflection from oriented inclusion needles in the basal plane perpendicular to the c-axis[GIA][IGS]. Cabochon cutting is required to display the chatoyant slit. The phenomenon is documented but uncommon per IGS. Most encountered cat's-eye kunzite enters collector hands rather than commercial trade.
The absence of asterism or color-change variants is part of the species' identity. Kunzite is single-phenomenon in commercial commerce, with the manganese chromophore driving a fixed pink-violet response that does not shift between daylight and incandescent illumination, distinguishing it from the chromium-vanadium chromophores in alexandrite or color-change garnet that do[Gem-A][GIA].
Some material shows weak orange-pink fluorescence under longwave UV, with rare specimens exhibiting brief phosphorescence after UV exposure. Both are diagnostic identifiers for the species rather than value drivers, and both reinforce the photochemistry that underlies the species' fade hazard[IGS][SSEF].
Species identity synthesized from the authoritative sources cited below.