Gemstone Heat Evolution: Sri Lanka's Historical Transformation

Nestled within the rich tapestry of Sri Lanka's gemstone history is a captivating practice that has endured for centuries – the art of gemstone heat treatment. In this blog, we journey through time to explore the evolution of this ancient technique, from rudimentary methods to the modernised processes that have turned discarded stones into treasures.

Dating back to hundreds of years, the practice of heat treating gemstones in Sri Lanka has deep roots. Early on, it was discovered that exposing rubies and pink sapphires to fire for a few hours could transform their blue tint into a more vibrant red. The heat treatment involved simple means – fuelled fires reaching temperatures around 400 degrees Celsius – but the impact was significant.

Thai Influence and Local Mastery:

In the late 1970s, Thai dealers entered Sri Lanka's gem scene, buying geuda and milky sapphire rough. Initially mysterious, these stones were claimed for fish tanks and Terrazzo flooring. The truth emerged – in Thailand, they were heated at 1700–1800 degrees, resulting in stunning royal blues.

By the 1980s, Sri Lanka adopted high-temperature heat treatment, mastering the art with insights from Thai expertise. By the late 1990s, transformed stones were returning, resplendent and perfected.

Evolution of Methodology:

Traditionally, gemstones were treated in small clay kilns fuelled by coconut husks and a blowpipe. Though imprecise, it required skill to predict gemstone reactions. Modern electric kilns now provide precise control over temperature and exposure time, enhancing color predictability.

Timing and Imperfections:

Heat treatment occurs before gem cutting to avoid expanding inclusions or fissures, preventing cracks. Unfortunately, natural imperfections are inevitable, making heat treatment crucial for enhancing gemstone aesthetics.

Conclusion:

The story of gemstone heat treatment in Sri Lanka is a blend of ancient wisdom and modern precision. From rudimentary fires to contemporary kilns, this practice continues to reveal the true brilliance within these precious stones. As we marvel at the transformed gems, we recognise the delicate dance between tradition and innovation defining Sri Lanka's gemstone treatment legacy.