gemmology.dev – Cambodia – Pailin Sapphire and Battambang Ruby

Introduction

Cambodia produces two geologically distinct types of corundum: basaltic sapphire
and ruby from Pailin Province (northwestern Cambodia), and small-scale marble-hosted
ruby from the Battambang area. The Pailin field sits in the same Southeast Asian
alkali basalt province as Thailand's Chanthaburi-Trat deposits, just across the
border. Production was severely disrupted during the Khmer Rouge era (1975–1979)
and the subsequent civil conflict, interrupting supply for two decades.

Geological Settings

Two corundum-forming environments in Cambodia:

Pailin – Basaltic Province

Cenozoic intraplate alkali basalt field; same Southeast Asian province as
Chanthaburi-Trat (Thailand) and Ratanakiri (also Cambodia, for zircon)
Corundum transported to surface in basalt; concentrated in alluvial placers
High-Fe, low-Cr geochemical environment – same signature as Thai basaltic material
Adjacent to Bo Rai (Thailand); material from both sides historically mixed

Battambang – Marble-Hosted Ruby

Small-scale occurrence of marble-hosted ruby – geologically analogous to
Mogok and Vietnam marble-type deposits
Low-Fe environment; strong fluorescence expected
Much smaller production volume than Pailin
Geologically distinct from the Pailin basaltic deposits

Khmer Rouge Era Hiatus

Pailin Sapphire and Ruby – Diagnostic Features

Characteristics of Pailin basaltic corundum:

Colour

Sapphire: Blue to green, yellow, and parti-colour; broad range typical
of basaltic sapphires
Ruby: Dark red; comparable to Thai basaltic material but with subtle
differences in trace element ratios

Chemistry and Spectroscopy

High Fe: Basaltic geochemical profile – >600 ppm Fe typical
Strong 450/460/470 nm triplet: Fe-related absorption in UV-Vis spectra,
similar to Thai material
LWUV fluorescence: Weak; iron quenches chromium signal
Oxygen isotopes: Values consistent with basalt-related corundum

Inclusions

Basalt-suite minerals: zircon (with halos), feldspar, iron oxides (ilmenite)
Consistent with basaltic parentage – same mineral family as Thai material
No marble-hosted inclusions (no calcite, apatite, sphene)

Pailin vs Thai Distinction

Separating Cambodian Pailin from Chanthaburi-Trat:

Historical difficulty: Pailin and Bo Rai (Thailand) material was historically
traded together through Chanthaburi and often mixed; laboratory separation was
not routine
Modern LA-ICP-MS: Trace element ratio patterns (Ga/Mg, Fe/Ti, Cr/Ga) and
oxygen isotope analysis can discriminate Pailin from Chanthaburi with some
confidence; the separation is a laboratory-level task
Practical trade note: Material described as "Thai ruby" in the trade may
include Cambodian origin stone heated in Thailand

Cambodia – Pailin Sapphire and Battambang Ruby