This page contains archives of the ‘Did You Know’ series. 

Check back occasionally for further updates to continue to invest in knowledge.

Archive of ‘Did You Know’?


                    Research Consulting

Invest in Knowledge                        

Did you know? 


When fully hydrated, a compacted sodium bentonite makes an effective hydraulic barrier due to the high tortuosity of flow paths.


(Figure adapted from Hornsey W, Gates WP, Buckley J. 2009. Geosynthetic clay liners – Is the key component being overlooked?  GIGSA GeoAfrica 2009 Conference. Capetown, September 2009.)

Did you know?


Smectites are poorly crystalline minerals which cannot be easily characterized by traditional methods, despite more than 100 years of effort.  Accurate characterization requires multiple spectroscopic and physical techniques.  The result is an average crystal chemical picture.


Figure at right is one such estimation of the array of octahedral cations in the Nibost smectite as deduced from analysis of the infrared spectra.  The tetrahedral sheets have not been included in this representation.


See Gates 2008 Clays and Clay Minerals, 56:11-23 for further details.

Did you know? 

Pore-filling reactions in bentonites, due to alkaline-induced dissolution/precipitation reactions, can enhance the barrier performance of geosynthetic clay liners.


(Picture from Gates and Bouazza, 2010, Geotextiles and Geomembranes, 28,219-225 )

Copyright 2006-2014

Did you know? 

The strong water absorption capability of smectites underpins the fact that bentonites are one of the most useful industrial minerals.  Water is held in many different energy states, so that some is released easily, but some is retained strongly. 

(Figure adapted from Gates et al. 2012 J Physical Chemistry C. 116:5558-5570.)

Did you know? 

Bentonites are widely used as components of environmental barriers in landfills, tailings dams and impoundments. Not all bentonites behave the same when reacting with typical leachates in the environment, which means that each bentonite should be ‘compatibility’ tested and assessed for specific applications.

The above graph depicts the ratio of Fluid Loss at each concentration of NaCl to its value in deionised water. The fluid loss of even high performance bentonites can increase by 10—20 times in 5 M NaCl (about 10x the salinity of seawater).  Such behavior must be accounted for in designs by environmental engineers.

(Figure from Gates et al., submitted to the ACMS22 conference)

Did you know? 

Reflectance spectra from the Mars orbiter CRISM indicates the presence of smectites on the surface of Mars?  Careful comparisons with Earth-based laboratory studies indicates that aluminium-rich beidellite is present in areas like Nili Fossae and Mawrth Vallis.  (Figure adapted from Bishop et al. 2011 Clays & Clay Minerals, 59:376-397)