Beach and Shoreline Sands From Around the World

by Elizabeth H. Kennair and Bruce Railsback

 

METHODS
Collection

        The sands in this collection were sampled by many people with a variety of scientific backgrounds. Sands collected by LBR or collected under his direction were collected at a series of positons from below the water line to the top of the swash zone or the intertidal zone.

        This collection may include sands from beaches where "replenishment" had taken place (where sand was dredged offshore and delivered to the beach). We have not considered this to be a major issue because our goal is to use the sands as representatives of the regional geology and/or regional ecological setting, rather than as representatives of conditions on the beach itself.

Treatment

        Almost all sands shown on these pages have been washed to preclude precipitation of salt from the seawater collected with the sample, and to remove dissolved organic matter (DOM) in that seawater. The samples were rinsed three times with tap water and then three times with deionized water and then dried in an oven at 50 to 100 degrees C. In addition to removing salt and DOM, washing removes very fine (fine-silt-to-clay-size) grains, but it typically has only a slight effect on beach sands and shallow marine sands because they contain little very fine material.

        For a few mixed sands containing both siliciclastic grains and abundant modern carbonate grains, we have acidized a subsample to remove the carbonate component. The samples were acidized in concentrated HCl.

        The sands shown on these pages have not been sieved. Ideally, comparison of sands should be made between consistent size fractions, because composition varies with grain size. However, had we used one consistent size fraction, we would have lost some samples from our collection because they consisted entirely of grains coarser than the majority of sands.

        Some sands were photographed within 60 days of their collection, but most were photographed as much as 11 years after collection and had been stored in air-tight glass bottles.

Photography

        For our standard (non-microscopic) photographs, sands were photographed under blue lights using a Nikon Coolpix 995 digital camera on its macro setting and with a 10-second delay. The working distance was 47 cm. The sands were then placed under a Bausch & Lomb 0.7x-to-3.0x binocular microscope set to 0.8x, illuminated with a goose-necked desk lamp, and photographed using a Nikon Coolpix 990 digital camera inserted into one ocular with a Martin Microscope Mmcool s/n 0956 adaptor. The sands were photographed at uniform magnification using the camera's normal quality, slow, and macro settings and with a 10-second delay. The width of the field of view of a raw image was 10 mm. After cropping to eliminate dark and unfocussed margins, the width of the field of view of a typical image generated with the microscope and shown on these pages is 8 mm.

        All of the photographs were taken with the sand lying on a background with a uniform gray color. Raw images of large-scale (non-microscopic) views commonly showed that background much lighter when a dark sand was photographed and much darker when a light sand was photographed. The brightness of all raw images of large-scale (non-microscopic) views was modified using Adobe Photoshop to make the gray of the background approach its actual gray color, allowing comparison between the different sands of their relative brightness or darkness. No attempt was made to make the illumination of microscopic images consistent. The contrast of several microscopic images had to be lowered because otherwise the grains appeared to shine with a polish or wetness not true to their actual appearance.

        All sands were photographed dry. Sands were shaken or smoothed to yield a relatively uniform sand. Grains of very coarse sands had to be carefully packed to provide a uniform depth of field and focused image under the microscope. In a few cases, large pebbles were removed. Shiny black sands were photographed with a polarizing filter inserted in the light path because their images were otherwise black fields with bright points of light.


The title page and table of contents for this set of web pages
Sand Pic
e-mail to Railsback (rlsbk@gly.uga.edu)
Railsback's main web page
UGA Geology Department web page