Current Exhibit

Tiger's-Eye Quartz

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Close-up view of a large polished slab of quartz variety tiger’s-eye from the Marra Mamba Iron Formation of Western Australia. It measures more than 3 meters (10 feet) long, 50 cm (20 inches) wide and 5 cm (2 inches) thick. Photo: Emily Lane/GIA

The multicolored rock from the Pilbara region of Western Australia is extremely old – formed from iron-rich sediments deposited in ancient seas about two and a half billion years ago. After millions of years, the sediments crystallized to form layers of hematite, magnetite and jasper, seen here as red-orange, silver and green bands.

At some point, tectonic activity buckled the rock, opening fractures that became infilled with the fibrous mineral crocidolite. As the fibers were crystallizing, they were encapsulated by quartz. Iron oxides were also trapped by the quartz and imparted a golden color.

Like the sheen seen in silk, light reflecting off the golden quartz fibers produces a chatoyancy known as tiger’s-eye. This decorative gem material is commonly polished to make beads and large cabochons.

Exhibiting this amazing but fragile piece presented a challenge. Weighing 180 kg (400 lbs) and only 5 cm (2 inches) thick, any flexion would have caused it to break. A special metal bracket, custom-designed to cradle the bottom edge, was screwed into the reinforced wall. A strong crew carefully hoisted the massive piece into position and added the top brackets to hold it in place. Check it out in the video below.