Iroishi Checker
No. 061 / 141
ReferenceREFERENCE
Black SpinelContribute a photo

Black Spinel

ブラックスピネル · ぶらっくすぴねる
NaturalBlack / Gray
Gemological dataPROPERTIES
Hardness8
Specific gravity3.60
Refractive index1.718
Crystal system等軸晶系
Color rangeCOLOR RANGE

Opaque deep black with high lustre — hexcode #111113 to #1F1F22. The colour is uniform without variation; surface lustre ranges from sub-adamantine to vitreous depending on cut quality. The Thai 'black star spinel' (Chanthaburi 4-rayed asterism material) shows the same deep black body with a silvery-white 4-rayed star asterism on cut.

UV responseFLUORESCENCE
Long-wave
365 nm
Inert (no )
Short-wave
254 nm
Inert
Typical inclusionsINCLUSIONS
  • nclusions (the chromophore source) — produces the 4-rayed asterism in Thai Chanthaburi material
  • egative crystals — diagnostic spinel signature visible only on high-resolution surface imaging due to opacity
  • nclusion networks (rare in opaque material)
  • nclusions
Optical characterOPTICAL TRAITS
  • Refractive index 1.712–1.736 — singly refractive (where measurable through pinpoint surface contact; the opaque material limits standard refractometer reading)
  • Specific gravity 3.58–3.90 — the iron-saturated black material trends higher than other colour varieties
  • Mohs 8 — excellent durability
  • Opaque (high iron content produces full visible-spectrum absorption)
  • Sub-adamantine to vitreous polish lustre
  • Inert under both LW and SW UV
  • nclusions
What to look forID POINTS
  1. 01Mohs 8 hardness — separates from black tourmaline (Mohs 7) and black obsidian (Mohs 5–5.5) on scratch test
  2. 02Singly refractive (no ) — separates from black zircon (strong ) and most other black gem materials
  3. 03Specific gravity 3.58–3.90 — separates from black tourmaline (3.06), black obsidian (2.35–2.55), and black diamond (3.52)
  4. 04Lack of conchoidal fracture — separates from black obsidian (volcanic glass with characteristic conchoidal fracture)
  5. 05Lack of striations or columnar structure — separates from black tourmaline (characteristic vertical striations)
  6. 06High sub-adamantine polish lustre — distinctive of black spinel versus the duller lustre of black onyx (Mohs 7 chalcedony)
Stones it gets mistaken forSIMILAR STONES
Black Tourmaline (Schorl)
Black Tourmaline (Schorl)
ブラックトルマリン（ショール）
Black tourmaline (schorl Na(Fe²⁺₃)Al₆(Si₆O₁₈)(BO₃)₃(OH)₄, Mohs 7, SG 3.06, RI 1.624–1.658, doubly refractive uniaxial negative, characteristic vertical striations and columnar prismatic crystal form, opaque deep black with sub-vitreous lustre) versus black spinel (Mohs 8, SG 3.58–3.90, RI 1.712–1.736, singly refractive isotropic cubic, no striations, octahedral or massive crystal form, opaque deep black with sub-adamantine lustre). The vertical-striation test is unambiguous: black tourmaline shows characteristic deep vertical striations on prism faces while black spinel shows clean polished surfaces without striation. The hardness difference (Mohs 7 versus 8) is decisive on a scratch test. The specific-gravity difference (3.06 versus 3.58–3.90) is clean on hydrostatic balance. The lustre difference (sub-vitreous tourmaline versus sub-adamantine spinel) is visible to the trained eye. Black tourmaline trades at $5–$50 per carat versus black spinel at $5–$80 per carat — comparable pricing.
Black Zircon
Black Zircon
ブラックジルコン
Black zircon (ZrSiO₄, Mohs 6.5–7.5, SG 4.6–4.7, RI 1.810–2.024 — among the highest of all gem minerals, strongly doubly refractive uniaxial positive tetragonal with dramatic 0.039, characteristic of back edges visible at 10×, opaque to translucent deep black) versus black spinel (Mohs 8, SG 3.58–3.90, RI 1.712–1.736, singly refractive, no ). The test is unambiguous: black zircon shows dramatic of back edges visible without magnification on larger stones while black spinel shows no oubling' is a classical diagnostic test in gemology coursework.
Care & handlingCARE
  • Mohs 8 — excellent durability for daily wear including ring and bracelet use
  • Ultrasonic cleaning generally safe
  • Steam cleaning acceptable
  • Storage in a soft pouch
Market notesMARKET
PRICE RANGE

Sri Lankan Ratnapura commercial black-spinel faceted stones at $5–$50 per carat for 1–3 carat stones. Thai Chanthaburi material at $10–$80 per carat. Thai 'black star spinel' (4-rayed asterism cabochons) at $50–$500 per carat. Tanzanian Mahenge material at $10–$60 per carat. Mogok Burmese material at $20–$150 per carat. Luxury-house finished jewelry incorporating black-spinel pavé (Chanel Café Society pieces, Cartier black-spinel pavé bracelets) trades at $5,000–$100,000+ per piece, but the black-spinel content represents only a small fraction of the price compared with the design, gold/platinum work, and brand premium.

Note: Disclosure as 'natural spinel' or 'black spinel' is the trade standard; heat treatment is not typically applied to black material (the iron chromophore is already saturating). Disclosure as 'star spinel' for the Thai Chanthaburi 4-rayed asterism material. The major luxury-house adoption (Chanel, Cartier, Tiffany, David Yurman, Lorraine Schwartz) drives premium positioning for branded pavé jewelry while the commercial loose-stone market remains accessible. Origin documentation is rarely required for black-spinel jewelry given the low per-carat pricing.

BackgroundBACKGROUND

Black spinel is MgAl₂O₄ in the cubic isometric system, coloured by saturating Fe²⁺ and Fe³⁺ (typically 5–15 wt% FeO+Fe₂O₃ — the high iron content makes the term 'ceylonite' or 'pleonast' historically applicable for iron-saturated spinel varieties). The opaque deep black colour with high lustre and the Mohs 8 hardness combine to produce a gem material that competes effectively with black diamond for pavé and central-stone use in fine jewelry — at dramatically lower cost. The singly-refractive isotropic-cubic structure produces uniform reflection without or aceting capacity scaled substantially from the early 2000s as luxury houses adopted the material; Chanel's 2003 Café Society high-jewelry collection (Patrice Leguéreau atelier, 18 Place Vendôme) is a landmark commercial use.

Origin & historyORIGIN & HISTORY

Origins

aceted-stone market.

History

Black spinel appears in classical Indian gemological tradition — the Sanskrit 'Ratna-Pariksha' (Buddhabhatta c. 6th century CE) mentions it as a protective amulet stone and seal-engraving material under the term 'sphatika-mani.' The Mughal seal-engraving tradition (16th–18th century, the Imperial workshops at Agra, Delhi, and Lahore) used black spinel alongside red and pink spinel for inscribed signet rings and stamp seals. The medieval and Renaissance European trade incorporated some black spinel under the broader 'pleonast' or 'ceylonite' iron-rich spinel category without distinguishing it commercially from red and pink varieties. Mineralogical classification: the term 'pleonaste' was coined by René Just Haüy in his 1801 'Traité de Minéralogie' for the iron-aluminate spinel (Mg,Fe)Al₂O₄ end-member; the term 'ceylonite' references Sri Lankan provenance for iron-rich black spinel. The breakthrough modern commercial era began in 2003 when Chanel's Café Society high-jewelry collection (Patrice Leguéreau atelier at 18 Place Vendôme) prominently featured black-spinel pavé and central stones, establishing the precedent for luxury-brand adoption. Cartier, Tiffany & Co., David Yurman, Lorraine Schwartz, and other major houses followed through the mid-2000s and 2010s. The 2010s 'minimalist black gem' engagement-ring trend (parallel to the salt-and-pepper diamond and black diamond trends) further consolidated the commercial position. The 2016 AGTA addition of spinel as August birthstone covered all colour varieties including black.

Lore & symbolism

August birthstone since 2016 (AGTA addition). The classical Sanskrit 'Ratna-Pariksha' tradition (Buddhabhatta c. 6th century CE) treats black spinel as a protective amulet and 'evil-eye' deflector — the Mughal seal-engraving tradition extended this protective association. Modern metaphysical traditions (Melody 1995, Hall 2003) place black spinel on the root chakra for grounding, protection, and 'shadow work' psychological integration. The Chanel 2003 Café Society high-jewelry collection narrative gives the variety a luxury-fashion-history association with Coco Chanel's signature black-and-white aesthetic.

OBSERVATION TOOLS · 2 ITEMS

Tools to confirm this stone

Tools that help confirm Black Spinel. Tap any item to jump to the matching section on the gem tools page.

References
最終確認日
2026年4月28日
参 考 文 献

本ページの物性値（屈折率・比重・硬度・結晶系等）は、上記の権威ある一次資料を相互参照して編集しています。最新の鑑別研究の進展により値が更新される場合があります。