hexagonal Synthetic synthetic emerald (overgrowth on natural seed)

Lechleitner Emerald (Overgrowth) (Overgrowth Crystal)

Be3Al2Si6O18:Cr,V

Crystal Structure

CDL Notation

 #! Species: Lechleitner Emerald (synthetic overgrowth on natural beryl seed)
#! System: Hexagonal (6/mmm)
#! Habit: Colourless natural beryl core with green synthetic hydrothermal skin
hexagonal[6/mmm]:({10-10}@1.0 + {0001}@0.6) > ({10-10}@1.1 + {0001}@0.7)

Crystal System hexagonal

Point Group 6/mmm

Crystal Forms (4)

{10-10} {0001} {10-10} {0001}

Quick Facts

Hardness

7.5

Specific Gravity

2.67

Refractive Index

1.565

Optical Character

Uniaxial -

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Physical Properties

Crystal Systemhexagonal

Hardness (Mohs)7.5

Specific Gravity2.67

CleavageImperfect basal

FractureConchoidal

LustreVitreous

Optical Properties

Refractive Index1.565

Birefringence0.006-0.009

Optical CharacterUniaxial -

Dispersion0.014

Pleochroismstrong: Vivid green (ordinary ray) / Bluish-green to colourless (extraordinary ray)

FluorescencePatchy UV response possible (core and overgrowth differ)

Origin & Identification

OriginSynthetic

Growth MethodHydrothermal-overgrowth-on-natural-seed (synthetic Hydrothermal Cr+V-rich Beryl Overgrowth Deposited On Natural Colourless Beryl Seed — Goshenite Or Pale Aquamarine)

ManufacturerJohann Lechleitner (Innsbruck, Austria)

First Produced1960

Diagnostic FeaturesColourless beryl core visible under 10x loupe (transmitted light) — the most immediately apparent feature; lighter colourless goshenite/aquamarine core visible inside green rim; crackled interface — at junction between natural seed and synthetic hydrothermal overgrowth a characteristic crackled or crazing texture develops ("crackled skin" in gemmological literature); different inclusion suites in core vs overgrowth — natural beryl core retains own inclusions (two-phase, growth tubes); synthetic skin shows hydrothermal features (nail-head spicules, chevron zoning); Cr distribution concentrated in outer zone only (Schmetzer et al. 1981 — Cr content analysis confirms synthetic origin of colouring layer); UV fluorescence: mosaic or patchy response possible (natural core vs synthetic skin); FTIR: seed beryl and overgrowth may show different water-related absorptions

Colours

Vivid green (Cr + V chromophores in hydrothermal overgrowth)

Common Inclusions

Colourless beryl core (diagnostic)Crackled interface between core and overgrowthNatural inclusions in core; hydrothermal features (nail-head spicules) in synthetic skin

Notes

CRITICAL CHEMISTRY FIX per VERIFIED.md Conflict 2 (F-01/REJ-02): R10 source listed incorrect formula Be3Al2(SiO3)6:Cr+V — this is a chain-silicate notation and is chemically incorrect for beryl (a cyclosilicate). Correct formula: Be3Al2Si6O18:Cr,V. Applied here per mandatory correction. Multiple API-verified papers: Schmetzer, Bank & Stahle 1981, Gems & Gemology 17(2):98 (DOI 10.5741/gems.17.2.98) [VERIFIED]: "The Chromium Content of Lechleitner Synthetic Emerald Overgrowth" — Cr concentrated in outer synthetic zone. Journal of Gemmology 1964 (DOI 10.15506/jog.1964.9.8.267) [VERIFIED]; Eppler 1968 (DOI 10.15506/jog.1968.11.4.120) [VERIFIED]; Schmetzer & Bank 1988 (DOI 10.15506/jog.1988.21.2.95) [VERIFIED]. Colourless core is definitive diagnostic — absent in natural emerald. Crackled interface is definitive — absent in natural.