Exceptional Fire Agate--"A Member of the 100 Carats Club"

Exceptional Fire Agate--"A Member of the 100 Carats Club"
Aqua Calientes, Sonora, Mexico
The world's only known fire agate deposits fall within two general areas-the Sonoran Desert region, stretching from southwest United States to northern Mexico, an area starting 100 miles north of Mexico City and lying between two north-south mountain ranges, the Sierra Madre Occidental and the Sierra Madre Oriental. These areas were subjected to extensive volcanic activity mostly during the Tertiary Period, 24 to 36 million years ago, relatively recent by geologic standards.

With colors often more vibrant than opal and less directional, fire agate is also more durable for daily wear. Not a well known gem, fire agate, a variety of chalcedony, is thought to form by volcanic activity when hot water saturated with colloidal silica and iron oxide invades cavities in the host rock below the earth's surface. During the cooling process chalcedony with iron oxide begins to grow on any available surface with many shapes and colors being formed by the mineral impurities. Known as schiller, the alternating silica and iron oxide layers, diffract and allow light to pass and form interference of colors known as "fire". The iron oxide is what gives this gem its characteristic brown body color. Polishing fire agate is done in such a way as to follow the natural contours of the stone until only the fire is visible.

The present example is "world-class" by anyone's definition. Easily 10 times the size of most fire agates commercially available, it could easily be mounted as a stunning brooch, pendant or belt buckle. Contour polished to follow the botryoidal growth, the expert polishing reveals a rich range of orange, red, russet, yellow and green hues with an astonishing iridescence. This is a truly unique offering for the serious mineral or gem collector. Weighing approximately 160.28 carats and measuring 54.0 x 41.0 x 12.83 mm