Geuda (ගෙවුඩ, pronounced gay-yoo-dah [needs IPA]) is a form of the mineral corundum, or sapphire, found primarily in Sri Lanka. Around 70%-80% of gems mined in Sri Lanka belong to geuda varieties.

Geuda. Geuda is considered one of the most improbable gem minerals due to the fact that it can be heated to produce excellent blue, fancy yellowish-orange, or pink sapphires. They can be translucent to semi-transparent, whitish, semi brownish, milky, or silky in appearance.

Simply put, the Geuda material is heated to just below its melting point, where the crystal lattice is expanded to it maximum and bonds between molecules are as “wide open” as they can be. The heat caused the silk to dissolve and release titanium into the crystal lattice of the sapphire. Titanium is the main cause of blue color in sapphire.

Ruby and sapphire of natural or synthetic origin can be heat treated to improve asterism; to remove asterism or silk; to improve, add, or remove color; and even to alter imperfections. At least nine distinct processes can be identified, although several m a y occur simultaneously.

Heat treatment of “Geuda” has become more prominent in Sri Lanka since late 1970 with enhanced knowledge to convert “Geuda” into premium blue colour sapphire. Uva province also consists of many gem varieties, including “Geuda.” Passara, Lunugala, Badalkubura, Monaragala, Wellawaya and Mahiyangana areas are famous for various types of “Geuda”.

Geuda The Sri Lankan geuda sapphire is a pale, translucent, and, until the discovery of heat treatments, useless variety of sapphire . Once heat treatment techniques were developed, this colorless gem could be turned into a striking blue stone.

Inclusions of Geuda sapphire samples from Sri Lanka show a feature of milky appearance. In this study, the samples can be divided into two groups, based on inclusion appearance, i.e., silk and cloud. Silk inclusions appear intersecting of silk along the crystal structure.

Sep 11, 2024 · Geuda is a sapphire variety that demonstrates a phenomenon known as colour change. In its natural form, geuda typically exhibits a milky or cloudy appearance, which is in stark contrast to the clarity and brilliance that are typically associated with gemstones.

Oct 31, 2018 · GEUDA SAPPHIRE: THE PAST, PRESENT, AND FUTURE OF A TRANSFORMATIVE GEMSTONE. Despite humble beginnings, geuda sapphire revolutionized the jewelry industry through its transformation from insignificant rock to dazzling gem.

Oct 22, 2021 · Sri Lanka is one of the famous countries for geuda gemstone which has the potential to convert into premium blue color through heat treatment. There are several types of geuda varieties and their subcategories (for example Diesel geuda could be subdivided into young, normal thick, very thick depending on its appearance under transmitted light).