amorphous Simulant opal simulant (glass-based)

Slocum Stone

Formula Borosilicate glass with internal laminated metallic interference layers

Crystal Structure

CDL Notation

 #! Species: Slocum Stone (borosilicate glass opal simulant)
#! System: Amorphous (glass)
#! Habit: Massive glass with internal metallic interference lamellae
amorphous[glassy]:{massive} | phenomenon[play_of_color:metallic_lamellae]

Crystal System amorphous

Point Group none

Crystal Forms (1)

{massive}

Quick Facts

Hardness

5.0

Specific Gravity

2.4

Refractive Index

1.48

Optical Character

Isotropic

Physical Properties

Crystal System: amorphous
Hardness (Mohs): 5.0
Specific Gravity: 2.4
Cleavage: None
Fracture: Conchoidal
Lustre: Vitreous

Optical Properties

Refractive Index: 1.48
Birefringence: 0
Optical Character: Isotropic
Fluorescence: None (glass; no OH absorption)

Origin & Identification

Origin: Simulant
Manufacturer: John Slocum (USA); later Kyocera/Inamori produced similar imitation opal products
First Produced: 1974
Diagnostic Features: Lath-like scaly metallic laminae visible at 30-60x magnification (vs mosaic sphere-stack domains in natural and Gilson opal); high SG 2.40-2.50 (floats opal; sinks in di-iodomethane); no FTIR OH absorption; glass substrate conchoidal fracture; no hot-point odour; isotropic

Characteristics

Colours

Colourless with metallic iridescent colour play (interference colours from metallic lamellae)

Common Inclusions

Flat lath-like metallic laminae (critical; visible at 30-60x)

Notes

Borosilicate glass with deposited thin metallic film laminations internally; proprietary process. Directly API-verified: Farn 1979, Journal of Gemmology 16(5):295 (DOI 10.15506/jog.1979.16.5.295) [VERIFIED]: "Imitation Opal — Slocum Stone" — metallic lath/scaly appearance documented explicitly. Key diagnostic suite versus opal: (1) scaly metallic laminae visible at 30-60x (vs mosaic patchwork of sphere stacks in natural opal and Gilson synthetic opal); (2) high SG 2.40-2.50 vs natural opal 2.00-2.20 and Gilson ~2.07 — hydrostatic SG measurement is immediately diagnostic; (3) no OH/water absorption in FTIR (natural opal is hydrous 5-10% H2O; Slocum has none); (4) conchoidal fracture on edges (glass substrate). Note on manufacturer: Slocum original patent 1974; Kyocera/Inamori produced similar products. Target: precious opal (play-of-colour).