Porosity plays a clearly important role in geology. It controls fluid storage in aquifers, oil and gas fields and geothermal systems, and the extent and connectivity of the pore structure control fluid flow and transport through geological formations, as well as the relationship between the properties of individual minerals and the bulk properties of the rock. In order to quantify the relationships between porosity, storage, transport and rock properties, however, the pore structure must be measured and quantitatively described. The overall importance of porosity, at least with respect to the use of rocks as building stone was recognized by TS Hunt in his “Chemical and Geological Essays” (1875, reviewed by JD Dana 1875) who noted:

> “Other things being equal, it may properly be said that the value of a stone for building purposes is inversely as its porosity or absorbing power.”

In a Geological Survey report prepared for the U.S. Atomic Energy Commission, Manger (1963) summarized porosity and bulk density measurements for sedimentary rocks. He tabulated more than 900 items of porosity and bulk density data for sedimentary rocks with up to 2,109 porosity determinations per item. Amongst these he summarized several early studies, including those of Schwarz (1870–1871), Cook (1878), Wheeler (1896), Buckley (1898), Gary (1898), Moore (1904), Fuller (1906), Sorby (1908), Hirschwald (1912), Grubenmann et al. (1915), and Kessler (1919), many of which were concerned with rocks and clays of commercial utility. There have, of course, been many more such determinations since that time.

There are a large number of methods for quantifying porosity, and an increasingly complex idea of what it means to do so. Manger (1963) listed the techniques by which the porosity determinations he summarized were made. He separated these into seven methods for …

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Characterization and Analysis of Porosity and Pore Structures

A descriptive classification of cross-stratified units is proposed based on six objective criteria, and diagnoses are given for fifteen distinct kinds of cross-stratified unit recognised with their aid. The origin of each kind is discussed in the light of existing observational, experimental, and theoretical studies. A three-fold genetic classification of cross-stratified units is tentatively outlined in which apparent origin and physical properties are closely correlated.

The classification of cross‐stratified units. with notes on their origin

Preface 1. Background 2. Microstructures of sedimentary rocks 3. Microstructures of igneous rocks 4. Microstructures of metamorphic rocks 5. Microstructures of deformed rocks Mineral symbols used in this book Glossary of microstructural terms.

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A Practical Guide to Rock Microstructure

Mudstones make up the majority of the geological record. However, it is difficult to reconstruct the complex processes of mud deposition in the laboratory, such as the clumping of particles into floccules. Using flume experiments, we have investigated the bedload transport and deposition of clay floccules and find that this occurs at flow velocities that transport and deposit sand. Deposition-prone floccules form over a wide range of experimental conditions, which suggests an underlying universal process. Floccule ripples develop into low-angle foresets and mud beds that appear laminated after postdepositional compaction, but the layers retain signs of floccule ripple bedding that would be detectable in the rock record. Because mudstones were long thought to record low-energy conditions of offshore and deeper water environments, our results call for reevaluation of published interpretations of ancient mudstone successions and derived paleoceanographic conditions.

https://science.sciencemag.org/content/sci/318/5857/1760.full.pdf

Accretion of Mudstone Beds from Migrating Floccule Ripples

http://romanportland.net/files/doc/seminar2008/jan_elsen_seminar2008s.pdf

Microscopy of historic mortars—a review

1. Introduction. In the case of nearly all branches of science a great advance was made when accurate quantitative methods were used instead of merely qualitative. One great advantage of this is that it necessitates more accurate thought, points out what remains to be learned, and sometimes small residual quantities, which otherwise would escape attention, indicate important facts. Since it applies to nearly all branches of geology, it is necessarily a wide subject, but so connected together that it seems undesirable to divide it. My object is to apply experimental physics to the study of rocks. At least six different kinds of physical questions are involved, some of which have been sufficiently studied, but others require experiments which would be very difficult to carry out, and all that I can now do is to endeavour to deduce plausible results from what is known. In doing this, it may be necessary to assume cases sufficiently simple for calculation, which may but imperfectly correspond to natural conditions, so that the results may be only approximately correct. In some cases, facts seem to show that there are important properties connected with subsiding material which cannot be explained in a satisfactory manner. Notwithstanding this, it appears desirable to do the best that I can with the material at my disposal, hoping to lead others to do what I intended to do, and correct such errors as are now unavoidable. In order to clear the way for subsequent detail, I describe a few general facts.

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On the Application of Quantitative Methods to the Study of the Structure and History of Rocks

If a piece of that part of the calcareous grit just below the coralline oolite, which contains numerous agatized shells, be dissolved in hydrochloric acid, we obtain portions of agatized shells, and a quantity of sandy matter, which without further examination would naturally be thought to be merely sand, and such it has hitherto been considered. When however examined with a microscope, it is at once seen to contain a very large quantity of reniform bodies, which are evidently not sand, but some kind of minute organisms converted into agate. The mere occurrence of minute agatized shells in this deposit would certainly not be a fact worthy of being laid before this Society, but since they exist in such vast numbers as to constitute a very considerable portion of a well-known rock, and by the manner in which they occur are presented to us in a form that is additionally interesting, perhaps a detailed account of them will not be thought a subiect unworthy of attention.

The chemical composition of a specimen containing no large shells was determined by dissolving it in hydrochloric acid; and the fine muddy matter was separated from the coarser sandy portion by suspension in water and decantation; from which I found that we had in 100 parts—

This coarse matter consisted, in nearly equal proportions, of the reniform agatized bodies, and sand, whose particles varied in size from 1/100th to 1/2000th of an inch, the average being 1/200th, of which the great bulk was composed.

On the Microscopical Structure of the Calcareous Grit of the Yorkshire Coast

The calcareous grit is a sandstone containing a variable quantity of carbonate of lime, which lies just below the coralline oolite. Good sections of it may he seen at Filey, Gristhorpe Bay, and Scarborough. A great part of it is only a sandstone containing a variable quantity of calcareous matter, hut a considerable portion contains a great deal, and is much hardened by the infiltration of agate, which has silicified many of the shells and the wood, and filled the chambers of many of the ammonites. It is to this part of the bed that I wish to call attention.

If a piece of it be dissolved in hydrochloric acid, we obtain portions of agatized shells, and a quantity of sandy matter, which, without further examination, would naturally be thought to be merely sand, and such it has hitherto been considered. When, however, examined with a microscope, it is at once seen to contain a very large quantity of reniform bodies, which are evidently not sand, but some kind of minute organisms converted into agate. The mere occurrence of minute agatized shells in this deposit would certainly not be a fact worthy of being laid before this Society, but since they exist in such vast numbers as to constitute a very considerable portion of a well-known rock, and, by the manner in which they occur, are presented to us in a form that is additionally interesting, perhaps a detailed account of them will not be thought a subject unworthy of ...

https://pygs.lyellcollection.org/content/pygs/3/1/197.full.pdf

Henry Clifton Sorby

Papers

On the Application of Quantitative Methods to the Study of the Structure and History of Rocks

On the Microscopical Structure of the Calcareous Grit of the Yorkshire Coast

On the Microscopical Structure of the Calcareous Grit of the Yorkshire Coast

2022 Henry Clifton Sorby Award