Description
Blue chalcedony consists mainly of silicon dioxide (SiO2). It measures 7 on the Mohs' hardness scale and has a specific gravity of around 2.58 ~ 2.64. It appears as light blue, deep blue or blue tinged with a hint of yellow-green due to the presence of chrysocolla. Nicknamed the "Taiwan Sapphire", it is often made into rings and earrings because of its elegant color and translucent appearance. It is the most valuable of the gemstones produced in Taiwan. Blue chalcedony can lose its color due to oxidization or heat so it needs to be stored away from high temperatures or direct sunlight. Deposits are mainly found in Taiwan's eastern coastal mountain range around the Doulan mountains and the Fongbin region in Hualien County.

Mineral Formation
Blue chalcedony is formed when heated solutions containing Silicon Dioxide (SiO2) settle in the holes and fissures within Andesite agglomerates. The blue color is due to the chrysocolla content. 

Geographic Distribution
Baliwan in Hualien County's Fongbin Township, the Matailin Mountain and Chenguang-ao Mountain between Hualien and Taitung; as well as Doulan Mountain and Cili River in Taitung County's Donghe Township.

Mining History
Records indicate that Blue Chalcedony veins had been found on Doulan Mountain in Taitung County's Donghe Township during the Japanese colonial period. In 1964 a Blue Chalcedony vein was discovered at an altitude of 700m on Jihanala Mountain in the upper reaches of the Cili River's southern branch in Donghe Township. Known as the "Doulan Old Mine", this was the first Blue Chalcedony vein to be officially mined. Another vein was found in the Chenguang-ao Mountain region of the Coastal Range in 1966 while another vein was found upstream of Baliwan River in Hualien County's Fongbin Township. The discoveries fueled a prospecting craze in blue chalcedony during the 1960's and 1970's. Many people would venture into the river valleys of eastern Taiwan after heavy rains and typhoons to search for chalcedony ore washed out by the rain. Most of the easily accessible blue chalcedony veins have now been mined out and this together with increased environmental awareness means there are no longer any large-scale mining operations.

Applications
(1) Made into rings, earrings, brooches and necklaces.
(2) Making of handicrafts.

National Museum of Natural Science