Gibbsite

Formula: Al(OH)3

Colour: White, light gray, light green, reddish white; reddish yellow (impure)

Lustre: Vitreous, Sub-Vitreous, Pearly, Dull, Earthy

Hardness: 2½ – 3

Specific Gravity: 2.38 – 2.42

Crystal System: Monoclinic

Name: Named by John Torrey in 1822 in honor of Colonel George Gibbs (1777-1834), of Newport, Rhode Island, USA. Gibbs was a wealthy import merchant who was a geologist and mineralogist. He helped found early scientific societies for mineralogy and geology and wrote several scientific articles on geology, mineralogy, and agriculture. He amassed the finest mineral collection in the USA up to the 1810s and the collection was eventually purchased by Yale University where it was an excellent nucleus for its research and museum collection.

Type Locality: Richmond, Berkshire Co., Massachusetts – USA

Polymorph of: Bayerite, Doyleite, Nordstrandite, UM1990-28-OHF:Al

Commonly as nodular white masses in laterite.