Canteras ? Mexican Opals in Matrix: Spectacular Cabs of Fire Book by Jack Hobart Fire opals from south-central Mexico fill cavities in volcanic matrix. They are often polished in cabochon (cab) form, generally shaped like half an egg, referred to as canteras by the miners. These opals are often transparent, showing internal features much like agates. The difference is that they exhibit a spectacular rainbow of color in patterns that range from sheets to patches, columns, tiny points called pin fire plus reflections off surfaces within the matrix cavity. Closeup photography using the new computer technique called focus-stacking brings the entire opal cab into sharp focus, revealing features not noticed previously. Canteras - Mexican Opals in Matrix, Spectacular Cabs of Fire calls attention to these wonders as a photo-filled book containing just enough text to introduce each subject form and explain each image. Many span entire pages in order to show fine detail. A goal is to demonstrate the collect ability of these opals, much as agates are collected. This is made easier, since these opals are much less expensive than gem opals from Mexico and Australia. This is the first serious book to be published about Mexican opals. It includes enough text to explain opal features, but the words don't get in the way of the photography.Chapters include collect ability, colors, patterns, matrix (its color and pattern), typical forms, and specific forms: eyes (eggs), ribbons, internal surfaces, crystal clusters, inclusions and oddities. The latter include contraluz, hidden recognizable shapes, changes in pattern when viewed in indirect light, and unusual fire patterns from internal surfaces. Some of these have not been previously identified and documented. In fact, one unique opal was loaned to the GIA for study. These are polished after removing their outer matrix, retaining the meandering shapes of their cavities. 88 pages