Visual Bank
Image credit: Scott Brande
Purposes and Content of the Visual Rock Bank
visual - dominated by images and icons that represent properties
classification chart portion for the identified rock
links to image galleries and external resources
Simplified Classification of the Common Sedimentary Rocks
A simplified classification of the common sedimentary rocks is at the bottom of this page, and here.
Organization of the Visual Rock Bank
This guide to the common sedimentary rocks includes one or more examples of each rock type in the classification chart. Click the label link for a web page on the rock type. The rock types below are arranged in the order of the simplified classification.
mineral precipitates
clastic / detrital / fragmental
organic carbon
Mineral Precipitates
Many different minerals occur as components of sedimentary rock.
Some sedimentary rock may be dominated by minerals that crystallize by precipitation from solution, either by
inorganic chemical reactions (e.g., in fresh, brackish, or seawater), or
through biochemically-driven reactions by organisms in their cells or immediate environment.
In this simplified classification, only the minerals that form a significant part of the sedimentary rock are included here.
CaCO3 (calcium carbonate) occurs commonly as calcite or aragonite
(Ca,Mg)CO3 (calcium magnesium carbonate) occurs as dolomite
NaCl (sodium chloride) occurs as halite
SiO2 (silicon dioxide) occurs as quartz
Fe2O3 (iron oxide) occurs as hematite
mineral precipitates
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
mineral precipitates
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
mineral precipitates
Clastic
Weathering of material at the surface of the earth results in the release of mineral grains and/or fragments from a host outcrop. This loose material may then be mobilized andtransported across the landscape in various ways, eventually coming to a stop through deposition. Such deposits of loose material may be transformed into sedimentary rock (lithified). Examples of this category of common sedimentary rock follows.
clastic - broken, as in pieces of rock broken from an outcrop
detrital - particles removed from a host rock and transported away
clastic
Click labeled link below image for web page.
clastic
Click labeled link below image for web page.
Image credit: James St. John
Organic Carbon
A familiar carbon-rich sedimentary rock is coal. The origin of of the vast continental coal deposits is from the partial decay, burial, and preservation of the remains of land plants.
The transformation of once-living plants into coal requires conditions of increasing temperature and pressure during burial. A simplified sequence of sedimentary rock corresponds develops as temperature and pressure increases from surface conditions to those present thousands of feet below the surface of the earth.
peat
lignite
bituminous coal
anthracite
organic carbon
Click labeled link below image for web page.
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
Image credit: James St. John
Click image to enlarge.
Classification of Common Sedimentary Rock
Nature's production over time of mineral matter and its change through weathering is prodigious and widespread. A consequence of the heterogeneous composition of the planet is a bewildering diversity of chemical compounds and weathered fragments in sedimentary rock.
The simplified classification table presented below focuses on features that may be observable without additional equipment (e.g., no hand-lenses, thin-sections, polarizing microscopes). As noted before, an advantage of digital online media is that images and video may be processed (e.g., zoomed) to partially substitute for the lack of hand lenses and low power microscopes.
