Inside Simple Rocks Lurks a Riot of Color

Viewed in the right light — and very close up — slices of stone turn into a riot of color. These jewel-like images are no secret in the world of geologists, but University of Padova professor of petrography Bernardo Cesare is bringing them to light for those who don't contemplate rocks every day.

By slicing rock and other materials into thin slices and photographing them with a microscope equipped with specialized filters, Cesare creates a stained-glass effect out of even drab rocks. These photomicrographs, as they're called, have a scientific purpose: investigating how a rock formed, what minerals it is made of, and what changes it underwent after its formation.

LiveScience talked to Cesare about how he came to see the artistic merits of such research and his favorite rocks to put under the microscope.

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Cesare is now working with a company to distribute his photographs on canvas in the United States. When available, ordering information will be on Cesare's website at http://www.microckscopica.org/.

LiveScience: When and how did you realize that these photomicrographs could be art?

Cesare: I am somewhat cautious about the use of "art" for my photos. I prefer to leave this to the viewers. In any case I tend to think that the artist is the rock, or nature: What I do is to find the right rock and "give" it the beautiful colors it can display. I am kind of a reporter. [See Cesare's photographs]

I started to take photomicrographs of rocks for aesthetic purpose more than 20 years ago, but it has been much more recently that I started a semiprofessional artistic activity by sending images to international competitions, and having them showcased worldwide. The turning point virtually coincided with the purchase of a good digital camera for my microscope — and corresponds to the start of my Web gallery.

LiveScience: The images are beautiful. Where do the colors come from?

This is the most difficult thing to explain. First of all I wish to point out that these colors — called interference colors — are actually seen looking down into a microscope, and are not a result of some image post-processing.

The colors are produced by the propagation of polarized white light inside the minerals. The speed at which the light travels through minerals varies based on the wavelength of the light. Because of this difference in speed, the white light that enters the crystal loses some wavelengths and is white no more when it exits.

The color depends on the type of mineral and on the thickness of the sample, but an additional complexity is that colors change when the rock slice, or "thin section," is rotated under the microscope.

This is the story made short. But in my images there's something more. As I said I don’t modify colors after the photo has been taken, but I play with interference colors until I obtain a pleasant combination by rotating the specimen, rotating the polarizing lens, and adding a plate called the "red tint plate," which introduces color contrast, into the light's path.

LiveScience: Can you predict from looking at a rock with the naked eye what shapes and colors will appear in the photomicrographs?

To some extent I can predict the shapes if the rock is one I have already seen, or similar. However, in most cases the microscopic view discloses an incredible small world that one would never expect. So I always look forward to seeing the thin section of a rock, because the naked eye is way too limited: The subjects depicted in these images rarely exceed 3 millimeters. Sometimes I make a casual discovery: I didn't know anything about a particular rock — "Ocean Jasper" from Madagascar — until I had a bead of it cut and a thin section made. Under the microscope it is incredible, and it has become one of my favorite subjects. [Watch Life Rocks the Earth: Biologic and Mineral Evolution]

As concerns the colors, this is the creative part. Once I have found the rock with the right shapes and textures, the "artistic" side of my work is to modify the interference colors until I like the composition of the image. When it happens I take a picture. Otherwise I move to another thin section.

LiveScience: You've also used this technique with synthetic materials such as plastic and nylon. What inspired you to do that? How do those materials look different from rocks?

The inspiration came from the photographic Lab technician, Claudio Brogiato, who told me and my Master thesis colleague that nylon provided exciting micrographs. This occurred in 1987, and after that I practiced quite a lot with nylon, but also with other plastic materials. Their colors come from the fact [these synthetic materials] are deformed, by tearing or molding.

The main difference with rocks is in the distribution of colors: In deformed plastic objects colors show continuous changes, like in a rainbow. Conversely, in rocks, each mineral usually (with some exceptions) corresponds to a patch of uniform color, which may change abruptly passing to the adjacent patch.

LiveScience: Are the photographs difficult to capture?

With digital photography the shooting process has become much easier, because you can immediately see the result of the shoot, and can easily control exposure and white balance in order to get a photo that most faithfully reproduces the colors that are observed under the microscope. For my work the main limit of digital cameras is now resolution.

However, capturing a photo is only the final stage of a longer work that is the choice of the right subject. In order to have a good image, not only do you need a good camera, you need the right rock, a carefully made, clean and clear thin section, and a good microscope that provides a sharp image.

LiveScience: Are there any rock types in particular you love to photograph, or patterns you like to see?

This is a difficult question. In principle, all rocks are exciting under the microscope in different ways. But I find it more difficult to work with sedimentary rocks, and therefore most of my images come from igneous and metamorphic rocks [rock types are named for how they form], which are also those I spend researching most.

Among them, two of the most photogenic samples are "Ocean Jasper" from Madagascar and a charoite-bearing schist [a type of metamorphic rock] from Yakutia, Russia. The first is a microscopic garden of flowers, the second provides the idea of flow in rocks, with blocky crystals surrounded by a curved and folded matrix. Rocks provide an incredible variety of patterns, from regular forms and straight lines to curves and waves; similarly, the distribution of colors is highly variable. One thing I like and look for are intimate intergrowths of crystals, which provide intricate patterns of repeating colors.

LiveScience: What's the most unusual or far-flung rock that you've photographed?

Actually the most unusual subjects I have photographed aren't real rocks, but slags artificially produced during the smelting of ores to extract metal. Owing to the rapid cooling this material contains crystals with very strange shapes resembling trees, called dendrites. Dendritic crystals also occur in natural rocks, but I haven't yet found the right sample.

The most far-flung rock is still in my wishes: I know that meteorites have amazing textures, but haven't yet had the chance to take photographs of some.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.