New Mexico Geological Society Annual Spring Meeting — Abstracts

A recent study of adobe, pressed-earth block, and rammed-earth production in New Mexico shows that more earth building materials are made and used in New Mexico than in any other state in the USA. In 1988 adobe production slightly exceeded three million bricks and production of pressed-earth blocks rose to about 730,000. Preliminary results from 1989 indicate a 5-10% increase in production over the previous year.

Analyses of soil mixes used by 42 commercial producers in New Mexico show that the mixes were made up of varying proportions of different size material. The average size composition was 67% sand-and-larger, 27% silt, and 6% clay material. Clay mineralogy of soil mixes varied, but the clay-size fraction commonly consists of about equal proportions of expandable clay minerals (smectite and mixed-layer illite/smectite) and non-expandable clay minerals (kaolinite, illite, and chlorite). Chlorite was present in only one sample and only in a very small quantity. Calcite (CaCO₃) was nearly ubiquitous, particularly in the clay and silt-size fractions. Analyses of 25 soil mixes show that the soluble part (principally calcite) of mixes averaged 10%.

Analyses of mud construction materials from other parts of the world exhibit quite different clay mineral suites. The two samples from the Peoples Republic of China (PRC) contained significant chlorite content. Two samples from the Mideast (Egypt and Israel) contain halite, indicating seawater or animal wastes was mixed with the mud. Another sample from Israel contained mostly kaolinite and little else. The Chinese adobe also contains significant calcite in the <2µm fraction; whereas the Egyptian, Israeli, and a sample from Ventura, California, contained none.

Climates and production techniques in other areas of the world differ significantly from those in New Mexico. Because clay mineral suites are dependent on the original parent material, but more on the environment(s) leading to the formation of mud deposits, ancient climates, sources of muds, and construction techniques can be identified.