Sand Gallery Update: Looking at Interesting Sands from eBay
Over the past couple of years, our Sand Gallery Updates have featured science teachers who use microscopes in conjunction with sand activities in their classroom. These posts have also featured the many ways that sand impacts our everyday lives. Along the way, our readers have pointed out to us interesting sand samples that can be purchased online. Recently, while going through some of the readers’ sand recommendations, we realized that all of the suggested sand samples were available from sellers on eBay, so we purchased a handful of these interesting sand samples.
Fluorescent Sand Mineral Capital of the World
We were directed to a supply of sand that comes from Franklin, New Jersey. This Borough of New Jersey, located in Sussex County, is home to over 150 minerals, many of which fluoresce when exposed to ultraviolet light. This particular sample is brown when viewed in natural daylight conditions, but when the sand is exposed to shortwave ultraviolet light (254 nm), it fluoresces green and orange.
For an ultraviolet light source, we used a handheld Spectroline ENF-280C, which has both longwave (365 nm) and shortwave (254 nm) ultraviolet bulbs in the same lamp housing.
To examine the sand under shortwave lighting conditions, we poured the sample into a small weighing boat, then passed the shortwave lamp over the sand. Upon exposure to the shortwave ultraviolet light, the sand grains fluoresce, with most of the sand grains emitting vibrant orange and green color:
Capturing an image of this particular sand sample using a stereomicroscope under shortwave ultraviolet light conditions was a bit challenging. For starters, the UV lamp was difficult to integrate into the light path of the stereomicroscope because of its size. The lamp had to be propped up at an angle and allowed to rest on the side of the stereomicroscope’s objective. Using the Nikon DS-FI3 camera, we increased the camera’s exposure sensitivity due to the low light levels produced by the fluorescing sand grains. We also made sure that our sample was being photographed in a completely dark environment.
A Gem of a Sand
This sand was described to us by a reader as super-cool, and after taking a closer look at it, we would have to agree. The sample has a striking deep purple color, and is composed of almost 100% garnet sand grains. Based on the seller’s description, the sand comes from St. Maries, Idaho, which makes sense, because the star garnet is Idaho’s official state gemstone.
In examining this sand using the stereomicroscope, you will notice that most of the grains are rounded and there is very little dust. Based on the morphology, we suspect that this sample is probably sourced from the St. Joe River, which runs through St. Maries, Idaho.
We were also intrigued by the uniformity of color of this sample, and decided to take a look at the chemistry of these sand grains using scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS). For garnets in general, the crystal structure and color is dependent on the combination of atoms that are substituted in the X and Y sites of this general formula X3Y2(SiO4)3. Based on the color and the SEM/EDS data, this sample appears to fit into the almandine/spessartine variety of garnets.
White Sands of New Mexico
This sand sample comes from White Sands National Park in New Mexico, the world’s largest gypsum dune field. A reader brought this particular sample to our attention because of its chemistry, stating that sand is commonly made up of silicon dioxide (SiO2), or quartz-based. The white sands of New Mexico are somewhat rare, geologically speaking, and are composed mainly of calcium sulfate (CaSO4 2H2O).
As it turns out, there are two samples of this sand available from the Microscopy Society of America’s Sandbox collection, each from a different location within White Sands National Park: one is from a collection site just off of Highway I-70; the other is labeled Doña Ana County.
As you can see, the individual sand grains are entirely white, and because of the unique chemical makeup of this sample, we decided to take a closer look using SEM/EDS. Based on the elemental EDS data, this sand is indeed mostly calcium sulfate.
Sand from Operation Overlord
There were a couple of historically significant sands recommended to us. The two historically significant sand samples purchased from an eBay dealer were shipped individually in black boxes, which contained a small glass vial of each sand, sealed at the top with a tiny cork. One the sands is from Normandy Beach, France, and the other is from the island of Iwo Jima, Japan; both sites where the sand was collected have historical ties to World War II. Because the sand quantity is relatively smaller in each of the vials, we poured the contents into a weighing boat for photographing, then returned the samples to their original vials.
We thought that this is a clever way to bring together a not-always-obvious pairing of subjects: historical world events and geology. As it turns out, geology (and geologists) played an important role in planning what was referred to by the Allied forces as Operation Overlord, the invasion of Normandy Beach in 1944. The importance of geology in the planning of the invasion is explained in an article “Geology and the liberation of Normandy, France, 1944” by Edward P.F. Rose and Claude Pareyn, published in Geology Today. Below are quotes from Rose and Pareyn’s article describing the importance that geology played in preparation for the June 6, 1944 D-Day invasion.
“…the character of the beaches and the coastal cliffs was of particular concern. It was important that vehicles followed firm routes across the landing beaches and not become bogged-down. Accordingly, the beaches were analyzed in detail not only with regard to configuration and slope but also to distribution of patchy peat, clay, sand and shingle which formed the surface.”
This quote refers to “modern” sand on the beach:
“Geologists working with the Inter-Services Topographic Department…determined the general morphology of the beach: an offshore wave-cut platform of solid rock cut intermittently by deep navigable passages, bordered landward first by patches of plastic clay and peat overlain by a variable veneer of modern beach sand and, finally, by a storm beach of pebbles behind which fen-like deposits tended to form.”
In the 19th century, Normandy began to develop one of the first seaside resorts, and with it, a tourist trade. This would explain the description of modern sand making up a good portion of the beach. Sand would have been deliberately brought in from neighboring sources in order to establish a sandy beach for the tourists.
Iwo Jima is a volcanic island, and its name translates from Japanese meaning Sulfur Island (硫黄島, Iō-tō). The Battle of Iwo Jima became famous after publication of the Pulitzer Prize-winning photograph made by Joe Rosenthal, showing US soldiers raising the American flag on the top of Mount Suribachi. Rosenthal’s iconic photograph has appeared in many forms, including a sculpture in Washington, D.C, and on a U.S. postage stamp pictured below:
The sand sample from Iwo Jima has a glassy appearance, and is made up of mostly black and dark brown grains.
Since Iwo Jima is known as Sulfur Island, we wanted to know if the sand contained any sulfur. Doing a bulk analysis of the sand sample using SEM/EDS, we found that this particular sample does not contain any sulfur.
The samples featured in this article were purchased for less than ten dollars, and with the exception of the historically significant sands, came in quantities large enough to make multiple sand study cards. As you can see, and as many readers have pointed out, sometimes the sand beneath your feet can be used to tell an interesting historical story.
Thanks again to our readers who suggested these sands.