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Elbaite

Elbaite is a lithium-rich mineral species belonging to the tourmaline group, a complex borosilicate known for its wide range of colors, making it a popular gemstone.^[1] Its name derives from the island of Elba, Italy, its type locality, where it was first described in 1913.^[1] Elbaite forms primarily in lithium-bearing granitic pegmatites and is distinguished from other tourmaline species by its content of sodium and lithium.^[2]^[1]

Overview

Definition

Elbaite is a cyclosilicate mineral classified within the tourmaline supergroup, specifically serving as the lithium-rich end-member of this complex borosilicate group.^[3] As part of the tourmaline family, it shares the general structural framework of ring silicates characterized by boron incorporation, but elbaite distinguishes itself through its enrichment in lithium at the X-site, alongside sodium and aluminum.^[4] The mineral typically occurs as prismatic to acicular crystals exhibiting a trigonal prism habit, resulting in a triangular cross-section, with faces often longitudinally striated and hemimorphic terminations.^[4] These crystals can reach lengths of up to 1.6 meters and are renowned for their strong pleochroism, where the color intensity and hue vary significantly depending on the viewing direction due to anisotropic absorption.^[1] In relation to other tourmaline species, elbaite represents the Na-Li-Al dominant composition, contrasting with the Fe-rich schorl (Na-Fe-Al) and Mg-rich dravite (Na-Mg-Al) end-members, which reflect variations in octahedral site occupancy driven by geological conditions.^[5] This compositional distinction underscores elbaite's association with lithium-bearing pegmatites, setting it apart in both formation and gemological value. Elbaite was first described in 1913 by Waldemar Schaller from material collected at the type locality on Elba Island, Italy, where Russian mineralogist Vladimir Vernadsky proposed the name in 1914 to highlight its unique lithium content.^[1]

Etymology and History

The name "elbaite" derives from the island of Elba, Italy, where the mineral was first identified in pegmatite deposits.^[1] In 1914, Russian mineralogist Vladimir Ivanovich Vernadsky proposed the name for lithium-rich tourmalines from this locality, distinguishing them based on their chemical composition during studies of Italian specimens.^[4] American mineralogist Waldemar Theodore Schaller contributed to the initial description in 1913, analyzing samples from Elba's Rosina pegmatite near San Piero in Campo.^[3] Prior to its formal naming, elbaite was commonly referred to as "lithium tourmaline" due to its distinctive lithium content, a term used since the early 19th century for similar pegmatitic varieties following the discovery of lithium in 1817.^[6] By the 1920s, elbaite gained recognition as a distinct species within the tourmaline group, as mineralogists refined classifications based on end-member compositions and crystal chemistry, separating it from other tourmalines like schorl and dravite.^[1] This period marked increased interest in elbaite's piezoelectric properties, which had been observed in tourmalines since the late 19th century but found practical application in early 20th-century devices such as pressure sensors for hydraulic equipment.^[7] The evolution of elbaite's understanding reflects broader advances in mineralogy, transitioning from a general "lithium tourmaline" grouping to its status as a formally defined species in modern nomenclature.^[4] In recent years, the International Mineralogical Association validated a neotype specimen from Elba in 2025 to standardize its description, underscoring the mineral's foundational role in tourmaline studies.^[3]

Chemical and Structural Properties

Chemical Composition

Elbaite, a lithium-rich member of the tourmaline group, has the ideal chemical formula Na(Li₁.₅Al₁.₅)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH), which can be simplified to NaLi₃Al₆(BO₃)₃Si₆O₁₈(OH)₄.^[8]^[1] This composition reflects the general tourmaline structure XY₃Z₆(T₆O₁₈)(BO₃)₃V₃W, where elbaite occupies the X=Na, Y=Li-Al, Z=Al end-member.^[9] The defining feature of elbaite is its high lithium content, typically 1-4 wt% Li₂O, which distinguishes it from other tourmaline species like schorl (Fe-rich) or dravite (Mg-rich). Compositional variations arise from substitutions, such as Fe²⁺ replacing Li at the Y site or F substituting for OH at the W site, leading to minor deviations from the ideal formula. For instance, trace amounts of F (up to 0.10 wt%) and other cations like Mn or Fe can occur, influencing stability within the tourmaline structure. Elbaite forms solid solution series with other tourmalines, notably the elbaite-schorl series, which extends from Li-Al-rich compositions to Fe-rich schorl via the substitution 3YFe²⁺ → 1.5YAl + 1.5YLi, and the elbaite-dravite series, involving Li ↔ Mg exchange at the Y site from Na(Li₁.₅Al₁.₅)Al₆(Si₆O₁₈)(BO₃)₃(OH)₄ to NaMg₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₄.^[1]^[9] These series highlight elbaite's role in the broader tourmaline supergroup, where coupled substitutions maintain charge balance.^[12] The chemical composition of elbaite is typically determined using electron microprobe analysis (EMPA) for major elements or X-ray fluorescence (XRF) for bulk composition, often supplemented by secondary ion mass spectrometry (SIMS) for light elements like Li and B.^[9] Such methods reveal Li₂O contents ranging from 1-4 wt%, with an example analysis from Elba, Italy, showing 1.66 wt% Li₂O alongside 37.89 wt% SiO₂ and 43.85 wt% Al₂O₃.^[8]

Crystal Structure

Elbaite crystallizes in the trigonal crystal system with space group R3m, a symmetry shared across the tourmaline supergroup.^[13] This arrangement results in prismatic to acicular crystals that are often hemimorphic, reflecting the polar nature of the structure along the c-axis.^[14] The unit cell parameters for elbaite are approximately a = 15.91 Å, c = 7.13 Å, with Z = 3 formula units per cell.^[3] These dimensions define a rhombohedral primitive cell, though values exhibit minor variations (e.g., a ranging from 15.80 to 16.10 Å) influenced by compositional substitutions in the lattice.^[15] At the atomic level, elbaite's structure features double rings of six corner-sharing SiO₄ tetrahedra forming [Si₆O₁₈]¹²⁻ units, paralleled by isolated [BO₃]³⁻ triangles that link the framework along the c-axis.^[13] The Y and Z polyhedra are octahedral sites, with Y occupied by Li⁺ and Al³⁺ in roughly equal proportions and Z dominated by Al³⁺, creating a robust scaffold that supports the overall borosilicate architecture.^[16] A defining element of the tourmaline structure, including elbaite, is the [O|BO₃] complex, where each BO₃ triangle is uniquely coordinated to an interstitial oxygen atom, contributing to the mineral's stability and chemical versatility.^[17] The predominant polytype in elbaite corresponds to the standard 18 Å cell configuration, though disorder in the alkali cation sites can introduce structural variations, such as reduced symmetry in some zoned crystals. Relative to the broader tourmaline group, elbaite's structure uniquely accommodates Li in the X-site, facilitating extensive solid-solution series and enabling the color diversity observed in its varieties.^[13]

Physical and Optical Properties

Mechanical and Thermal Properties

Elbaite exhibits a Mohs hardness of 7 to 7.5, making it moderately durable for a silicate mineral.^[4] Its specific gravity ranges from 2.90 to 3.10 g/cm³, with variations primarily due to differences in lithium and other compositional elements.^[4] The mineral displays indistinct cleavage along the {11̅20} and {10̅11} planes, resulting in an uneven to conchoidal fracture.^[4] Elbaite is brittle in tenacity, prone to breaking under stress without significant plastic deformation.^[4] As a member of the tourmaline group, elbaite is pyroelectric, generating an electric charge in response to temperature changes due to its polar crystal structure.^[4] The linear thermal expansion coefficients are anisotropic, with values of approximately α⊥c = 3.86 × 10⁻⁶ °C⁻¹ and α∥c = 8.32 × 10⁻⁶ °C⁻¹ at room temperature, reflecting the trigonal symmetry.^[18] Elbaite demonstrates piezoelectricity, producing an electric charge under mechanical stress owing to its non-centrosymmetric crystal structure, as detailed in the crystal structure section.^[4] Historical measurements indicate piezoelectric coefficients on the order of several pC/N, with values varying by composition; for instance, the e₁₁ coefficient for elbaite is lower than in dravite but higher than in some iron-rich tourmalines.^[19]^[20] Chemically, elbaite shows resistance to acids, remaining stable in acid-to-neutral aqueous solutions, but it is soluble in fused alkalis under high-temperature conditions.^[7]^[21]

Optical Characteristics

Elbaite exhibits a wide range of colors, from colorless to vibrant greens, pinks, blues, and multicolored varieties, primarily due to trace transition metal impurities such as manganese for pink hues, iron for green and blue tones, and copper for neon blue shades.^[22]^[23]^[24] For instance, pink elbaite derives its color from Mn²⁺ substituting at the Y-site in the crystal structure, while green varieties result from Fe³⁺ in similar positions, with copper enhancing saturation in blue-green examples.^[24]^[25] The mineral displays strong pleochroism, a property where it shows different colors when viewed along different crystallographic axes, particularly pronounced in darker green and brown specimens.^[26] In green elbaite, this manifests as shifts from yellow-green to blue-green, while pink varieties may appear from pale pink to reddish along the ordinary and extraordinary rays.^[4]^[27] Elbaite is optically uniaxial negative, with refractive indices typically ranging from nω = 1.620–1.643 (ordinary ray) to nε = 1.600–1.622 (extraordinary ray), yielding a birefringence of 0.017–0.021.^[28]^[27]^[29] Its luster is vitreous to slightly resinous, contributing to the gem's appealing sparkle, and transparency varies from transparent to translucent depending on inclusions and crystal quality.^[4]^[30] Absorption spectra reveal characteristic features tied to chromophores; pink elbaite shows bands around 545 nm from Mn³⁺ intervalence charge transfer, while green types exhibit broad absorption below 430 nm and a band at 720 nm due to Fe²⁺ d-d transitions.^[31]^[25] Dispersion is low at 0.017–0.018, resulting in minimal fire compared to diamonds but sufficient for subtle color play in faceted stones.^[30]^[28]

Varieties

Color-Based Varieties

Elbaite exhibits a wide range of uniform colors due to trace elements substituting in its structure, leading to distinct varieties prized in gemology.^[26] Achroite is the colorless variety of elbaite, representing the pure lithium-aluminum end-member without significant chromophoric impurities that would impart hue.^[32] Its lack of color results from the absence of transition metal ions such as iron, manganese, or copper, making it a rare transparent form suitable for faceting despite limited demand compared to colored counterparts.^[33] Rubellite denotes the red to pink elbaite variety, where the coloration arises primarily from Mn³⁺ ions occupying octahedral sites, producing absorption bands that yield vivid raspberry-red to ruby-like tones.^[23] For gem-quality rubellite, the hue must remain stable and saturated without undesirable gray or brown overtones, often enhanced by low iron content to avoid muddying the color.^[26] This variety commands high value, with fine specimens exceeding several hundred dollars per carat.^[26] Indicolite is the blue variant of elbaite, spanning light sky-blue to deep sapphire-blue shades, attributed to intervalence charge transfer between Fe²⁺ and Ti⁴⁺ ions that absorb in the red and yellow regions of the spectrum. The intensity depends on the Fe:Ti ratio and overall trace levels, with purer blues free of greenish tinges being most desirable.^[32] Indicolite ranks among the most valuable elbaite colors, often surpassing rubellite in price for exceptional deep blues.^[26] Verdelite refers to the green elbaite, typically displaying olive to yellowish-green tones caused by Fe²⁺ ions.^[33] The yellowish cast often stems from combined Fe²⁺ and Ti⁴⁺ influences, distinguishing it from more emerald-like chrome tourmalines.^[22] While more abundant than pink or blue forms, high-quality verdelite with vivid saturation holds moderate to high gem value.^[26] Paraíba tourmaline is a striking neon blue-green variety of elbaite, characterized by vivid turquoise to electric-blue hues resulting from elevated Cu²⁺ (up to 2 wt% CuO) and Mn³⁺ contents, with Cu²⁺ producing broad absorption bands around 700–920 nm.^[22] Although first discovered in the Paraíba region of Brazil, similar Cu-Mn-rich compositions occur elsewhere, and while predominantly elbaite, rare occurrences in other tourmaline species have been noted.^[23] Its extreme rarity drives premium pricing, often reaching thousands of dollars per carat for clean, large stones.^[26] Among elbaite's color varieties, pink rubellites and blue indicolites (including Paraíba subtypes) are the most prized for gem use due to their rarity, saturation, and aesthetic appeal, far outpacing greens or colorless forms in market value.^[26]

Zoned and Special Varieties

One prominent zoned variety of elbaite is watermelon tourmaline, characterized by a pink or red core surrounded by a green exterior rind, often separated by a thin colorless zone.^[34] This zoning arises from sequential crystal growth during formation, where early stages incorporate higher manganese (Mn) relative to iron (Fe), producing the pink interior, while later stages see increased Fe availability, resulting in the green rim.^[35] The Mn/(Mn+Fe) ratio varies significantly across zones, typically ranging from near 1.00 in the core to as low as 0.10 in the rim, reflecting changes in the hydrothermal fluid composition available for crystallization.^[34] Bi-color and tri-color elbaite exhibit parallel growth zones of two or three distinct hues within a single crystal, such as colorless to pink transitions or black-blue-green sequences, driven by evolving compositional conditions in pegmatite pockets.^[36] These variations stem from progressive enrichment in volatiles and incompatible elements like lithium (Li), Mn, and fluorine (F) during pegmatite crystallization, with early zones showing higher sodium (Na) and lower Mn (e.g., Na₂O at 1.77–1.91 wt.%) and later zones displaying elevated Mn (up to 0.27 wt.%) responsible for pink coloration.^[37] In examples from the Cruzeiro pegmatite in Brazil, the zoning follows a schorl-to-fluor-elbaite trend, with Fe²⁺ decreasing and F increasing outward, mirroring the overall magmatic differentiation.^[37] Cat's eye or chatoyant elbaite is a rare variety displaying asterism, where a sharp band of light moves across the cabochon surface due to reflection from parallel, needle-like inclusions.^[38] These inclusions, often acicular structures or fine growth tubes aligned parallel to the c-axis, create the silky effect, as observed in specimens from Minas Gerais, Brazil, where microscopic examination reveals trichites and irregular two-phase features enhancing the phenomenon.^[38] Copper-bearing elbaite, particularly the neon-blue variants known as Paraíba-type, features vivid electric blue hues from copper (Cu) incorporation at the Y-site, often with pronounced zoning such as purple cores transitioning to blue bodies and green rims.^[39] Cu contents range from several hundred ppmw to over 1 wt.% (e.g., 0.30–1.17 wt.% CuO), far exceeding typical levels and producing absorption peaks near 700 and 900 nm that yield the intense color, distinct from the iron-induced blue of standard indicolite.^[40] Zoning in these crystals correlates with trace element gradients, including higher Mn in purple zones (up to 4.69 wt.%) and Cu peaks in blue areas.^[40] While natural zoned elbaite dominates, synthetic versions have been grown in laboratories for research, such as hydrothermal synthesis of Mn-rich or dravite compositions to study structural properties under high pressure, though no gem-quality synthetics exist commercially.^[26]^[41]

Geological Occurrence

Formation Processes

Elbaite primarily forms through the crystallization of late-stage magmatic fluids in lithium-cesium-tantalum (LCT) type granitic pegmatites, where volatile-rich residual melts become highly enriched in boron (B), lithium (Li), sodium (Na), and aluminum (Al) due to extreme fractional crystallization of the parent granite magma.^[1]^[42] These pegmatites develop as coarse-grained intrusive bodies within granitic host rocks, with elbaite precipitating in the inner zones or pockets as the melt cools and differentiates, concentrating incompatible elements like Li and B.^[43] The process involves the exsolution of aqueous fluids from the crystallizing melt, which facilitates the growth of prismatic to acicular elbaite crystals in open cavities.^[44] Crystallization of elbaite occurs under relatively low-temperature conditions of approximately 350–550°C and low pressures around 2.4–3 kbar, typical of shallow crustal emplacement in pegmatite environments.^[42]^[44] During fractional crystallization, early removal of feldspars and micas depletes the melt of major elements, progressively enriching it in volatiles and trace elements, which leads to chemical zoning in elbaite crystals as growth conditions fluctuate with fluid composition and temperature gradients.^[36] This zoning reflects rapid changes in the availability of elements like Fe, Mn, and Ti from the evolving fluids within pegmatite pockets.^[43] In terms of paragenesis, elbaite commonly co-occurs with quartz, microcline feldspar, lepidolite mica, spodumene, and beryl in the lithium-enriched zones of LCT pegmatites, forming assemblages that indicate boron metasomatism and alkali enrichment.^[1]^[44] It may also appear in metamorphic schists through contact metamorphism adjacent to granitic intrusions or in high-temperature hydrothermal veins derived from pegmatite fluids.^[1] Secondary enrichment can occur via supergene weathering of primary deposits, though elbaite's high hardness (7 on the Mohs scale) limits its transport, resulting in rare alluvial concentrations.^[1]

Notable Localities

Elbaite's type locality is the Rosina pegmatite on Elba Island, Italy, where small pink and green crystals were first described in 1913, with a neotype sample defined from this site in 2025.^[1]^[45] Brazil, particularly the state of Minas Gerais, stands as the world's leading producer of elbaite, with significant output from pegmatites in the Araçuaí-Salinas district since the mid-20th century. Key sites include the Limoeiro, Xanda, Manoel Mutuca, Salinas, and Ouro Fino mines, which have yielded large green, blue, pink, and multicolored crystals, including watermelon varieties with pink cores and green outer zones, peaking in the 1970s and 1980s.^[46] In the state of Paraíba, the São José da Batalha mine near Salgadinho produced vivid neon-blue to turquoise copper-bearing elbaite, known as Paraíba tourmaline, starting in 1982 and gaining international attention by 1989.^[23] In the United States, San Diego County, California, hosted historic gem-producing pegmatites from the early 1900s, with notable output from the Himalaya, Tourmaline Queen, Stewart, and Pala Chief mines, featuring pink, green, and bi-colored crystals from rich pockets.^[47] Also in the US, Oxford County, Maine, is renowned for elbaite from classic localities such as Mount Mica and the Dunton Quarry, producing gem-quality green, pink, and bi-color crystals since the 19th century.^[1] Afghanistan's Paprok locality in Nuristan Province is renowned for large bi-colored elbaite crystals, often exhibiting pink cores with green or blue caps, extracted from pegmatites in the Hindu Kush mountains.^[48] Madagascar's Sahatany Valley near Ibity yields high-quality rubellite, the red to pink variety of elbaite, from granite pegmatites, with gemmy crystals prized for their saturated hues.^[49] In Mozambique, the Alto Ligonha pegmatite district in Zambezia Province has produced significant quantities of multicolored elbaite, including green and pink varieties, since the late 20th century.^[50] A significant recent discovery occurred in 1994 near O'Grady Lake in Yukon's Selwyn Mountains, Canada, where large green elbaite crystals up to several centimeters were found in lithium-rich pegmatites, marking a major North American source.^[51] In Nigeria, emerald-green verdelite has been mined from pegmatites in Oyo State since the early 2000s, contributing to the global supply of intense green elbaite.^[52] Many classic elbaite sites face depletion, such as the original Paraíba mines in Brazil, which were largely exhausted by the early 2000s after intense artisanal extraction, and historic California pockets that yielded finite high-quality material in the 20th century. Ethical sourcing concerns persist in artisanal mining operations, particularly in Brazil and Africa, where small-scale methods raise issues of environmental impact, worker safety, and community benefits.^[53]^[54]^[55]

Uses and Applications

Gemstone Applications

Elbaite, the lithium-rich variety of tourmaline renowned for its vibrant colors, is highly valued in gemology for meeting specific quality criteria that enhance its appeal in jewelry. Clarity plays a crucial role, with eye-clean stones preferred for lighter tones like pinks and blues, while darker greens and reds can accommodate minor inclusions such as thread-like cavities or fluid-filled tubes without significantly diminishing value.^[56] Color intensity is paramount, favoring vivid saturation in hues like rubellite pink or indicolite blue, where medium-light tones maximize brilliance; size further elevates desirability, as facetable material over 5 carats is scarce, commanding premiums due to the challenges in sourcing large, clean crystals.^[56] These factors align with the standard 4Cs of gem evaluation, emphasizing how exceptional color and clarity in larger specimens can transform elbaite into collector's pieces.^[26] Elbaite is typically cut as faceted gemstones to showcase its pleochroism and color depth, with popular shapes including ovals, pears, and rectangles oriented along the crystal's long axis to optimize light return.^[56] For varieties exhibiting chatoyancy—caused by parallel needle-like inclusions—cabochon cuts are employed to highlight the cat's-eye effect, particularly in green or multi-colored stones.^[26] Beads, often round or faceted, are another common form, strung into necklaces or bracelets to utilize lower-grade material while preserving the gem's multicolored charm in casual jewelry.^[26] Valuation of elbaite hinges on rarity and aesthetic appeal, with vivid pink rubellites fetching $300 to $1,000 per carat and neon blue Paraiba varieties—distinguished by copper content—$2,000 to over $20,000 per carat for top-quality stones between 3 and 5 carats (as of November 2025), far exceeding prices for common greens at $50 to $200 per carat.^[56] ^[57] ^[58] Crystals exceeding 10 carats in clean, saturated colors carry a substantial size premium, reflecting limited availability from pegmatite sources. Treatments are employed to enhance marketability, including low-temperature heating to lighten brown tones or improve blue-green hues, irradiation to boost pink saturation, and oil or resin filling of fractures to mask inclusions; the Gemological Institute of America (GIA) mandates full disclosure of such enhancements to maintain transparency in trade.^[59]^[56] Elbaite's prominence as a gemstone emerged in the 19th century, when improved cutting techniques and recognition as a distinct mineral separated it from misidentified emeralds, fueling its use in Victorian-era jewelry for mourning pieces and colorful accents.^[26] Brazilian discoveries, particularly in Minas Gerais during the early 20th century, dramatically increased supply, with the 1980s Paraiba finds introducing neon varieties that revolutionized the market and elevated global demand.^[60] Although hydrothermal synthetics can replicate elbaite's colors, they remain rare and non-commercial due to high production costs, easily distinguished from natural stones by the absence of characteristic inclusions like growth tubes, lepidolite crystals, or trichite fluids visible under magnification.^[59]^[26]

Industrial and Scientific Uses

Elbaite, a lithium-rich variety of tourmaline, has been employed in piezoelectric applications due to its ability to generate an electric charge under mechanical stress. In the early 1900s, elbaite crystals served as pressure sensors in hydraulic presses and electrical gauges.^[61] During World War II, thin wafers of electronic-grade elbaite were integrated into depth-indicating devices on submarine hulls, where compression from seawater pressure produced microcurrents to drive gauge mechanisms for precise sonar-related measurements.^[62] Postwar advancements saw its use in microphones, transducers, and phonograph pickups, though synthetic piezoceramics have since supplanted it owing to superior sensitivity. The piezoelectric coefficient d_{33} for elbaite is approximately 2 pC/N, reflecting its modest performance relative to modern alternatives.^[19] In scientific research, elbaite functions as a model mineral for investigating lithium diffusion mechanisms in silicates, leveraging its zoned structure to trace Li transport during crystal growth.^[63] Compositional zoning in elbaite crystals enables geothermometry applications, where elemental variations—such as increases in Li and Mn from core to rim—reveal temperature gradients and fractional crystallization in pegmatitic environments.^[36] These analyses provide insights into magma evolution without requiring direct temperature measurements, highlighting elbaite's role in reconstructing geological formation processes. Recent studies (2025) have explored elbaite in ZnO composites for photocatalytic CO₂ reduction, achieving 93.4% selectivity to fuels like CO and CH₄, with enhanced durability for environmental remediation.^[64] Industrially, elbaite finds minor application as a boron source in ceramics and glassmaking, where its composition lowers melting temperatures and acts as a flux to improve viscosity and thermal properties.^[65] Its pyroelectric properties, which produce charge changes with temperature variations, support limited use in radiation detection devices, such as early bolometers for infrared sensing.^[66] Modern developments explore elbaite's potential in microelectronics for compact sensors, capitalizing on its natural piezoelectric response. Additionally, copper-bearing variants, known as Paraíba-type elbaite, are under study for optical materials due to their unique refractive indices and color stability.^[67] Despite these utilities, elbaite's scarcity in high-quality crystals and high extraction costs restrict widespread industrial adoption, particularly when compared to abundant, low-cost alternatives like quartz for piezoelectric devices.^[62]

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Jul 22, 2025 · Elbaite, Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH), is a mineral species of the tourmaline supergroup. A formal description of the neotype ...
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Crystal Data: Hexagonal. Point Group: 3m. Crystals prismatic to acicular, with prominent trigonal prism and pyramid, to 1.6 m, commonly hemimorphic ...
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A lithium-tourmaline is called Elbaite. Elba Island, Italy, was one of the first localities where colored and colorless Li- tourmalines were analyzed. In 1914 ...
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Chemistry: (1). SiO2. 37.89. TiO2. 0.04. B2O3. 10.28. Al2O3. 43.85. FeO. 0.11. MnO. 0.11 ... (1972) Refinement of the crystal structure of elbaite and the ...Missing: formula | Show results with:formula
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Mineralogical Society of America. Handbook of Mineralogy. Revised 5/19/2017. Fluor-elbaite. Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F. Crystal Data: Hexagonal.Missing: structure | Show results with:structure<|control11|><|separator|>
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The general formula of tourmaline may be written as: XY3Z6T6O18(BO3)3V3W, where. X (≡ [9]X) = Na+, K+, Ca2+, □ (= vacancy); Y (≡ [6]Y) = Al3+, Fe3+,. Cr3+, V3+, ...
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Nov 15, 1988 · At room temperature it was found that for elbaite, 𝛼 a =3.86× 1 0 − 6 K − 1 and 𝛼 c =9.11× 1 0 − 6 K − 1 ; for schorl, 𝛼 a =3.48× 1 0 − 6 K − 1 ...Missing: properties pyroelectric piezoelectric
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[23]
Spectroscopy Characteristics and Color-Influencing Factors of ...
Oct 5, 2023 · The primary factors influencing the color of tourmaline were the absorption band at 720 nm caused by the Fe2+ d-d transitions and the 300 to 400 ...
[24]
Tourmaline Gem, Price, and Jewelry Information - IGS
Jul 10, 2025 · Does Tourmaline Show Pleochroism? Color Changes with Viewing Angle. Dark green and brown tourmalines exhibit particularly strong pleochroism, ...
[25]
[PDF] TOURMALINE Elbaite - GIA
Optical Character: Refractive Index: Birefringence: None. LWUV: SWUV: None. 0.017. Specific Gravity: 3.05. Pleochroism: Brownish yellow / Bluish green. None.
[26]
https://www.gemsociety.org/article/tourmaline-jewelry-and-gemstone-information/
[27]
Lets talk Gemstones: Tourmaline
The green elbaite crystals produced in Kashmir, India exhibit a specific gravity of 3.05, refractive indices of 1.622-1.643 and birefringence of 0.021.
[28]
Elbaite (Tourmaline) Gem Guide and Properties Chart
It was named for the colored and colorless tourmalines found on the picturesque island of Elba off the western coast of Italy. Although best known in shades of ...Missing: etymology | Show results with:etymology
[29]
[PDF] the optical absorption spectra of tourmaline: importaiuce of charge ...
Crystal-field transitions within Cr3+ and Mns+ are responsible for the colours of some deep- green and pink tourmalines (Manning 1969a,b); ... green tourmalines ...<|separator|>
[30]
Tourmaline - The Gemology Project
Oct 11, 2011 · The refractive index of tourmaline lies between 1.610 and 1.698 (usually between 1.62 and 1.64) with a birefringence up to 0.039 (usually 0.019 ...Missing: causes | Show results with:causes
[31]
16.14: Tourmaline - Geosciences LibreTexts
May 6, 2022 · Tourmaline is an extremely complex borosilicate that occurs in more than 100 colors. It is hard and durable and very well suited for jewelry.
[32]
Watermelon” tourmaline from the Paprok mine (Nuristan, Afghanistan
The Mn/(Mn+Fe) ratio, calcu- lated for each analytical point, ranges from ... Mn↔Fe the elbaite-component increases. The Mn content is in all charge ...
[33]
An Update on Tourmaline from Luc Yen, Vietnam | Gems & Gemology
Aug 11, 2017 · The green elbaite samples contained more iron (up to 4.88 wt. % FeO) than the pink elbaite (maximum 0.21 wt.
[34]
Gem Elbaite as a Recorder of Pegmatite Evolution: In Situ Major ...
Nov 8, 2021 · This crystal is characterized by sudden transformation from colourless to pink, which can represent full pegmatite magma evolution.
[35]
Insights from the compositional evolution of a multi-coloured, zoned ...
Jan 6, 2025 · This study compares the compositional evolution of a multi-coloured, zoned tourmaline crystal from the Cruzeiro pegmatite, BrazilMissing: bi- tri-
[36]
Cat's-Eye Brazilian Paraíba Tourmaline | Gems & Gemology - GIA
Microscopic examination revealed diagnostic irregular two-phase inclusions, trichites, and acicular (needle-like) features. The sharp cat's-eye effect was ...
[37]
Geographic Origin Determination of Paraíba Tourmaline - GIA
Copper-bearing tourmaline from Mozambique was first recovered in 2001, but its Cu content was not recognized until 2003, and it was not widely sold with its ...
[38]
[PDF] Chemical Variations in Multicolored “Paraíba”-Type Tourmalines ...
We concentrated on the analysis of element variations within single crystals of copper-bearing tourmalines, which contain pronounced color zoning and extensive ...
[39]
High-pressure study of dravite tourmaline - GeoScienceWorld
Oct 1, 2018 · Growing synthetic tourmalines >1 mm in diameter has not yet been achieved, and thus industrial applications require natural tourmalines ...
[40]
[PDF] A Preliminary Deposit Model for Lithium-Cesium-Tantalum (LCT ...
Fluid inclusion studies of various pegmatites suggest formation at ≈350–550 °C and relatively low pressures in the range of 3 kb. (London, 2008). Size ...
[41]
[PDF] Gem-Bearing Pegmatites: A Review - GIA
That is, tourmaline crystals may have black, opaque. (schorl) roots in the solid pegmatite and become pink, green, blue, etc. (elbaite) as they approach and ...<|control11|><|separator|>
[42]
[PDF] Formation of tourmaline-rich gem pockets in miarolitic pegmatites
If tourmaline crystallization is inhibited until the late stages of pegmatite ... Pressure-temperature estimates for the San Diego. County pegmatites, California.
[43]
Elbaite, the neotype material from the Rosina pegmatite, San Piero ...
Jul 22, 2025 · The unit-cell parameters are a=10.569(2), b=20.590(4), c=12.413(2) Å, and β=90.33(3)∘. The results from the structure refinement were ...
[44]
[PDF] Gem Pegmatites of Minas Gerais, Brazil: The Tourmalines of ... - GIA
Three of the most famous tour- maline localities in Brazil-Virgem da Lapa,. Salinas, and Ouro Fino-lie in this area (again, see figure 2) and are discussed in ...
[45]
Elbaite from Himalaya Mine, Gem Hill, Mesa Grande Mining District ...
Famous Mineral Localities: the Himalaya Dike System, Mesa Grande District, San Diego County, California. The Mineralogical Record, 8 (6) 461-474Missing: notable | Show results with:notable
[46]
Elbaite from Paprok, Kamdesh District, Nuristan, Afghanistan - Mindat
Does anyone know of...minerals from Elba—Napoleon's island—and especially elbaite, named of course for Elba, its type locality. But...see it still there, still ...
[47]
Rubellite from Maroando, Sahatany Valley, Ibity, Antsirabe II District ...
Rubellite from. Maroando, Sahatany Valley, Ibity, Antsirabe II District, Vakinankaratra, Madagascar ; Species: · Formula: ; Tourmaline var: Rubellite · A(D 3)G 6(T ...
[48]
Canadian Rockhound: Canadian Tourmaline - A New Discovery
Gem-quality tourmaline, mainly elbaite, was discovered near O'Grady Lake. Crystals are often pink/brownish pink, with some green, orange-brown, and blue, and ...
[49]
Elbaite from Oyo, Nigeria - Mindat
lepidolite from which rise two thin, gemmy blue-green elbaite crystals to ... Nigeria • Rough emerald imitation • Silicon inclusions...with hand tools ...
[50]
Around the world in luxury jewellery: Brazilian Paraiba tourmalines
Nov 24, 2015 · The frantic clamouring for Paraiba tourmalines that ensued led to the original mine being virtually depleted over the course of just a few years ...
[51]
Paraiba Tourmaline - Smithsonian National Museum of Natural History
The original mines have been depleted, and even though there is speculation that more deposits in the area have been found and will produce new material, it ...<|control11|><|separator|>
[52]
Artisanal Gem Mining in Brazil: A Source of Genotoxicity and ... - NIH
In this work, a study of environmental biomonitoring and routes of exposure to toxic metals in a region of artisanal mining was performed.Missing: elbaite depleted
[53]
Tourmaline Quality Factors - GIA
The gem is an elbaite tourmaline that comes from one area of Paraíba state in Brazil's northeast corner. Like many other Brazilian elbaites, Paraíba ...
[54]
Micro-Features of Tourmaline - GIA
No synthetic gem tourmaline exists. Tourmaline is a borosilicate mineral supergroup with a trigonal crystal structure and a wide range of chemical compositions.
[55]
[PDF] An Update on "Paraíba" Tourmaline from Brazil - GIA
During the 1990 Tucson gem show, prices for this material skyrocketed from a few hundred dol- lars to over $2,000 per carat in just four days. (Federman, 1990; ...
[56]
[PDF] ELBAITE | Celestial Earth Minerals
JEWELRY & DECORATIVE USES: With its substantial hardness (Mohs 7.0-7.5), a lack of cleavage that enhances durability and facilitates cutting, moderately high ...
[57]
Piezoelectric Crystals: The Key to Current Technology
Aug 5, 2024 · Thin wafers of electronic-grade crystals of the tourmaline-group mineral elbaite were used as piezoelectrical generators in the depth-indicating ...Missing: historical | Show results with:historical
[58]
Lithium and its isotopes in tourmaline as indicators of the ...
Oct 1, 2008 · In the present study, concentrations and isotopic ratios of Li in tourmaline are used to constrain the role of Li in the crystallization of ...
[59]
[PDF] Lithium - USGS Publications Warehouse
Aug 16, 2012 · Lithium, the lightest of all metals, is used in air treatment, batteries, ceramics, glass, metallurgy, pharmaceuticals, and polymers.
[60]
[PDF] Influence of chemistry on the pyroelectric effect in tourmaline - RRuff
These results indicate that the onset ofpy- roelectricity that is caused by anharmonic vibration of ions in the structure and high thermal expansion may occur ...
[61]
[PDF] “paraíba”-type copper-bearing tourmaline from brazil, nigeria ... - GIA
The Mulungu mine is located 5 km north- northeast of the town of Parelhas, and Alto dos. Quintos is situated about 10 km south of Parelhas. Although neither of ...