Samlot — also spelled Samlaut, transliterated variably from the Khmer — is a gem-mining locality in the western Battambang Province of Cambodia, near the border with Thailand. The deposit is part of the basaltic gem field that extends across the Cardamom Mountain region of western Cambodia and into the better-known Pailin field to the south. Samlot produces blue, blue-green, and green-blue sapphire of basaltic origin, typically with the colour profile and inclusion characteristics common to Southeast Asian basaltic stones. Production has fluctuated considerably with the political history of the region; the field operated principally as artisanal small-scale mining through the 1990s and 2000s following the political stabilisation of the Pailin region after the Khmer Rouge insurgency, with continued small-scale activity into the present.

Geology

The Samlot deposit, like Pailin, is hosted in alkali basalt of late Cenozoic age. The sapphires are xenocrysts — crystals carried up from the upper mantle and lower crust by the basaltic magma rather than crystallised from it — and are released by weathering of the host basalt into alluvial concentrations along streams and old terrace deposits. Mining is principally alluvial, working the gravels and weathered basalt with hand and small mechanical methods. Hard-rock mining of the source basalt itself is uneconomic given the low concentration of sapphire in the unweathered host.

The trace-element chemistry typical of basaltic sapphire — moderate to high iron, low titanium, generally low chromium — produces the characteristic colour and behaviour of Samlot stones. The high iron content tends toward darker, more saturated blues; the comparatively low chromium means colour-change behaviour is rare; and the iron-rich character typically produces stones that are somewhat darker and more inkily-toned than the cornflower blues associated with metamorphic sapphires from Sri Lanka or Madagascar.

The stones

Samlot sapphires are typically blue to blue-green to green-blue, with colour ranging from medium-dark to dark tones. Stones of strong, saturated, medium-toned blue are sought; very dark stones, the so-called 'inky' Australian-style basaltic blues, are present but commercially less attractive. Sizes are generally modest — most production is under five carats, with stones over ten carats relatively unusual. The crystal habit favours thinly tabular forms parallel to the basal plane, which constrains the cutter's options and produces a high proportion of cushion and oval cuts with shallower-than-ideal proportions.

Inclusions characteristic of basaltic origin include CO₂ negative crystals, columbite group minerals, and short rod-like silk; intersecting silk is rare and the asterism that arises from intersecting silk is correspondingly less common than in metamorphic Sri Lankan material. Heat treatment is standard for commercial Samlot stones, principally to improve colour clarity and reduce the visibility of silk. Untreated stones are present but require explicit disclosure and laboratory verification.

Production and trade

Samlot production has fluctuated over the past three decades. Active mining intensified in the late 1990s as the Pailin and broader western Cambodian region stabilised politically, and small-scale activity has continued through the 2000s and 2010s. Volumes are modest compared to the historic Pailin field; Samlot is generally regarded as a secondary deposit within the Cambodian sapphire context. The principal trade route runs from Cambodia into the Thai market through Chantaburi, Bangkok's main coloured-stone trading centre, where the stones are heat-treated, graded, and integrated into the broader Thai sapphire supply.

Origin documentation for Samlot stones is rare in the formal laboratory sense; the stones generally trade as Cambodian basaltic sapphires without specific mine attribution, and laboratories such as GIA, Gübelin, and SSEF will issue Cambodian origin opinions on stones whose chemical and inclusion profiles support that determination but rarely descend to specific Cambodian sub-locality.

Comparative context

Samlot stones occupy the same broad commercial tier as other Southeast Asian basaltic sapphires from Pailin, from Khao Ploi Waen in Thailand, and from the Daklak field in Vietnam. They sit below the metamorphic Sri Lankan and Madagascan stones in the typical commercial hierarchy and considerably below the rare metamorphic stones from Kashmir, Mogok, or fine Madagascan material. The category is best understood as workmanlike commercial sapphire — durable, attractive, and accessible — rather than as a competitor to the elite metamorphic stones.

In the trade

For dealers, Samlot stones are unlikely to appear under that locality name in the international trade; the more useful framing is 'Cambodian basaltic sapphire,' the trade category that includes Pailin and Samlot together. Pricing reflects basaltic origin: meaningful discounts to fine metamorphic stones of comparable visual appearance, with heat-treatment status standard and disclosure required for any unheated material.

Further reading

• GIA Gems & Gemology — basaltic sapphire articles and Cambodian field studies
• International Gem Society — sapphire origins and treatment
• ICA — Southeast Asian sapphire trade