The microscopic investigation of solid materials such as minerals, rocks, ores, technical and other synthetic products, in transmitted or reflected light, remains one of the classic, and to this day indispensable, mineralogical methods of analysis.
It provides a non-destructive way to characterize the properties of solid substances with relatively high spatial resolution.
Compared to the highly sophisticated modern analytical techniques, polarized-light microscopy has the unrivalled advantage to be efficient, fast and cheap.
(Michael M. Raith, Peter Raase, and Jurgen Reinhardt: Guide to Thin Section Microscopy)
Transmitted-light microscopy allows studying materials that are translucent in thin sections of ca. 0.03 mm thickness. Observation in the bright-field (plane-polarized light mode) reveals structural features and colours, which are not visible to the naked eye (Fig. 1a). When studying the thin section between two crossed polarizers (crossed polars mode), due to the commonly anisotropic behaviour of the crystalline constituents, manifold interference phenomena are observed. As a result, the fabric of the material appears in a variety of interference colours (Fig. 1b). Further diagnostic interference colour effects occur by inserting an accessory plate (quartz wedge, lambda-plate, lambda/4 plate) between the polarizers (Fig. 1c).
Figure 1: Thin section photomicrographs of a blueschist from Syros, Cyclades, Greece. The mineral assemblage comprises glaucophane, epidote, phengite, and quartz.
(a) Plane polarised light mode; (b) Crossed polars; (c) Crossed polars with lambda-plate. Size of views: 1 x 1 mm.
Microscopic investigation provides the scientist with fundamental insights into the phase content, fabric and formation of materials. The artist’s eye experiences an unknown and fascinating world of images, whose variety of colours and structures offers an unlimited source of inspiration.
Motifs found by chance can encourage design. Internal moods and ideas are, however, what guides the eye when looking for motifs. Ideally, the visual motifs correspond to the artistic intention; frequently, however, they only achieve the intended expressiveness through digital processing.
Digital photomicrographs of high resolution constitute the raw material for the artistic design. In the present case they are taken with a Canon EOS 70D digital camera mounted on a LEICA DLMP polarising microscope. A high-performance adapter (ASKANIA Mikroskop Technik, Rathenow) is used for connecting the digital camera to the photo tube of the microscope. The digital processing and artistic design of the photomicrographs are accomplished with the Adobe Photoshop software.
Objects of photomicrography are predominantly thin sections of rocks (magmatic, metamorphic and sedimentary rocks) and more rarely of technical materials and synthetic products. They originate from the comprehensive personal thin section collection and various teaching and research collections of the Steinmann Institute, University of Bonn.