Of the 3800 or so legitimate mineral species, fewer than 750 are typically well crystallized and attractive. Consequently, the tendency among CD producers, book publishers and web site operators has been to present only these more common minerals in photographs. While these efforts satisfy the beginner and those collectors only interested in the more common and aesthetic phases, many advanced collectors and serious amateurs are left without a reliable, visual reference source for virtually all of the uncommon and rare minerals. It is this significant majority of minerals that we have attempted to depict in this CD.
The vast majority of the minerals photographed in this CD were taken from the inventory
of Excalibur Mineral Company, the
largest dealer in rare species in the U.S. and, arguably, the world. The Excalibur
inventory contains more than 200,000 samples, and at any point in time, over 3000
different mineral species are in stock. These include high-quality specimens as well as
more representative material that the user could expect to collect or purchase for a
reasonable amount in the open market. The inventory's strength is in rare species, of
course, the major focus of this CD. The company's website is located at www.bestweb.net/~excalmin;
additional specimens are from the private collections of the authors, with a small number
obtained from colleagues.
In selecting material to be photographed, every effort was made to provide a reasonable
representation of the species in question, without resorting to many multiple photographs
of the same phase. We have endeavored, however, to present as wide a range of mineral
habits and appearances as practical for each mineral that exhibits a range of appearances.
In some instances, specimens are extremely small, many are unattractive, and some had to
be photographed using a scanning electron microscope in backscatter image mode to properly
identify the phase. To ensure reliability, material was often analyzed at the Excalibur
laboratory or elsewhere to confirm the species depicted.
Using visual means as a primary method of identification is not an acceptable nor scientifically valid means of identifying minerals. While many minerals exhibit characteristic appearances, many other common and rare minerals can frequently masquerade as other common or rare minerals. Thus, to use sight identification alone is to invite error!
However, information gathered from visual observations, when combined with other available data, (especially a mineral's location, associations, and habit), can help to confirm the presence of certain mineral species or narrow the list of possibilities. It is to this use that this CD is addressed. We have endeavored to present as wide a range of mineral habits and appearances as practical for each mineral that exhibits a range of appearances. The hyperlinks provided for major associations and localities should further assist in identification efforts.
Each specimen was photographed using a 35mm camera, occasionally with a microscope, and more rarely, with a Scanning Electron Microscope. Slides were prepared and scanned with a high-resolution scanner. Modifications to images were restricted to color balancing and cropping, and no "artificial" images were created using computer software. Commonly available digital cameras were not employed due their generally inferior resolution. This method yielded identical results as what would have been obtained using a sophisticated digital camera.
Numerous hyper-links were created in order to allow rapid movement among species, localities, mineral groups and associated species. Netscape Navigator is included with this CD so that an external web browser is not required. Virtually all of the photography and computer architecture was the work of Dr. Jeffrey G. Weissman over a period of nearly two years.
Specimen Descriptions and Localities
In addition to chemical composition, a brief description of each specimen is provided with the corresponding image in order to indicate to the user any features that may not be readily apparent. Also included are links to significant associations on that particular specimen, as well as links to the specific state or country of origin. We have attempted to make the specimen locality information as accurate as possible. Localities were checked against current maps and geopolitical databases, and an index by country or state, and then by province, region, or county, is also provided. This index is accessible from either the locality maps or from the hyperlink of the state or country noted in each photograph's caption.
Comments on quality of photographs
Image quality is a function of many factors, all of which come together to produce the images displayed on the monitor. These include specimen quality, photographic technique, image translation, and image retrieval and display.
Perhaps the most important factor is specimen quality. Certainly a distinct well-formed crystal will result in an image much superior to the same mineral found as a indistinct mass. During the course of photographing the minerals, we had available a wide range of specimens and specimen qualities, from the well formed crystal to the submicroscopic. The quality of the resulting images reflects this range. Many of the photographs reproduced on this CD give a good, even excellent (we hope!), assessment of the respective minerals. In contrast, no one is more disappointed in some of the resulting final images than we are for those minerals which are known or available only in minute masses or occur as submicroscopic inclusions or are otherwise indistinct. Why include these lesser images? The answer is to provide a record of the occurrence, and in some instances to illustrate the matrix of the mineral, which may be distinctive. In an effort to provide a complete record, such material has to be unavoidably included..
Modern photographic technique is well adapted for making suitable mineral photographs, as long as sufficient care is taken to insure adequate lighting, sufficient depth of field, and so on. The primary limitation is on achieving adequate magnification for some of the very smallest microcrystals. You may notice that an occasional photograph may appear fuzzy or indistinct, especially for those images having a scale bar length representing 0.05 cm or smaller. This represents the practical limit of the equipment used for most of the primary photography on this CD. Other concerns, such as film grain and film development were addressed by using slow film and a custom photo lab.
Image translation includes digitizing (scanning), file size adjustment and compression, contrast and brightness control, and color balance. Provided sufficient resolution is used in the scanning process, and careful monitoring of color balance is maintained, this part of the process has, for the most part, only a small impact on image quality. When specimens contain fine detail, such as those consisting of vary small granular or specular material, or contain small grains of one mineral as an association, the scanning and reduction process may lose some of this information. This is a limitation of the resolution of the monitor and of disk storage space, and until monitors can display significantly higher resolutions (for example, a display of 8000 x 6000 pixels, as opposed to a typical 1024 x 768 for a 17" monitor), this fine detail will not be reproducible. In addition, the size of these high resolution files will require much higher storage density, considering the large numbers of images. Once these limitations are overcome, then the true fidelity and sharpness of the film images of these 'difficult' specimens can then be displayed.
In a similar vein, the final image quality is only as good as the monitor it is displayed on. While a 14" monitor capable of 16 colors or 256 colors may be adequate, the best results will be on a monitor that can display 24 or 32 bit color depths and give at least 1000 pixels across the screen. Practically all 17" monitors and most recent 15" monitors should be capable of this requirement. Monitor performance can vary. Adjustment of monitor color balance, brightness, and contrast may be necessary to best view the images on this CD. See our digital color balance chart.
Comments on image manipulation
Every aspect of computer generated objects can be controlled and manipulated at will; this most certainly applies to computer-generated images and photographs derived from computer processing. This is no different than manipulating photographic images in a darkroom or in a camera, only more convenient. We have endeavored to faithfully produce images that represent the actual specimens as they would appear as viewed with the naked eye or under a microscope, with no enhancement or modification to the appearance of the specimen, except the processing necessary to translate the film image to a image capable of being displayed on computer monitors. Note that while we have taken liberties with removing distracting objects, such as dirt, smudges, or stray reflections, from the backgrounds of the images, we have not added or removed any information from the actual mineral images.
It is our belief that while computer manipulated photographs are a valid art form, once manipulated, images can no longer be considered photographs in the traditional sense. Thus we give here only reproductions of photographs of the many mineral species.
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