Pisolitic Bauxite Value Guide

Pisolitic Bauxite is a fascinating sedimentary rock formed 30-50 million years ago through intense tropical weathering that leaches silica to leave behind aluminum-rich minerals. Collectors prize these specimens for their distinct pea-sized spherical structures, known as pisolites, which serve as a visual record of ancient humid climates.

What affects the value of Pisolitic Bauxite?

• The clarity and definition of the individual spherical pisolites significantly impact the specimen's aesthetic appeal.
• The overall size and weight of the rock, with standard collector pieces typically valued between $10 and $12.
• The balance of mineral content, specifically the visual contrast between the Iron oxide staining and the lighter Aluminum oxide minerals.
• The structural integrity of the specimen, as well-preserved samples without excessive crumbling are more desirable.

How to Identify Pisolitic Bauxite?

• Look for the characteristic 'pea-sized' spherical structures called pisolites embedded within the rock matrix.
• Identify the presence of aluminum-rich minerals such as Gibbsite and Boehmite which give the specimen its composition.
• Check for a color palette typically ranging from reddish-brown to creamy white, indicating varying levels of Iron oxide.
• Verify the origin as the United States, where these specific 30-50 million-year-old formations are commonly sourced.

History of Pisolitic Bauxite

Bauxite is the primary ore for aluminum and was first discovered in 1821 by Pierre Berthier near the village of Les Baux in France. Pisolitic varieties are characterized by their pea-sized round structures, which form through the intense weathering of rocks in hot, humid climates where silica is leached away, leaving behind aluminum-rich minerals like gibbsite and boehmite.