Rocks, Gems, and Minerals of the Rocky Mountains by Garret Romaine

Rocks, Gems, and Minerals of the Rocky Mountains by Garret Romaine

Author:Garret Romaine
Language: eng
Format: epub
Publisher: Falcon Guides
Published: 2019-10-28T00:00:00+00:00


Fulgurite

This fulgurite from Boulder County, Colorado, formed when lightning fused quartz-rich sands.

PHOTO COURTESY OF THE IMAGE ARCHIVES, DENVER MUSEUM OF NATURE AND SCIENCE

Quartz, SiO2

Family: Quartz

Mohs: 7

Specific gravity: 2.65

Key test(s): Tubelike fused glass; rough exterior

Likely locale(s): Sandy deserts

Sand fulgurites are the result of lightning strikes hitting quartz-rich sand deposits. (Rock fulgurites result from lighting striking rocks, usually at the tops of mountains, and are less collectible.) The intense heat of the strike instantly fuses the quartz in the sand, usually in a tube that is rough on the outside and smooth, sometimes bubbly, on the inside. The resulting color is based on the melted material and is usually gray, light gray, or tan. Fulgurites can extend several feet into the ground, usually branching or tapering away eventually.

Look for fulgurites in any flat, open sandy desert or dune area where thunderstorms are common. Wyoming’s Red Desert would be a good place to look, or in Boulder County, Colorado.



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