Turquoise: Identifying and Collecting the Southwest's Iconic Gemstone - Softcover

Lynch, Dan R.; Lynch, Bob

Softcover

ISBN 10: 1647553865 ISBN 13: 9781647553869

Verlag: Adventure Publications, Incorporated, 2025

Inhaltsangabe

Explore the beauty and history of turquoise, one of the most celebrated and treasured gemstones of ancient and modern times.

Revered around the world, turquoise is a mineral with two histories: that of its formation and that of the people who have mined, traded, and treasured it. Turquoise is an icon of ancient civilizations and especially of the desert regions where it most famously appears. Uncover the history and the secrets of this coveted gemstone in Turquoise. Written by Dan R. Lynch with Bob Lynch, the authors of several books about rocks and minerals, this is the definitive guide to the sky-blue stone.

Begin by learning the natural history of turquoise, from how it forms to where it’s found. Dan and Bob present tips for finding and identifying turquoise, and they introduce turquoise look-alikes. Next, go in-depth on the human history of turquoise. You’ll learn all about buying and caring for turquoise, and you can glimpse our future with this gemstone of the American Southwest. Whether you’re a rockhound or someone who simply appreciates nature’s wonders, grab this book and get to know the storied mineral whose very name is a symbol of color.

Book Features

• Summary of the fascinating natural history
• Expert advice on how to find and identify turquoise
• Full-color photographs and maps
• Suggestions on what to do with turquoise

Über diesen Titel

Über die Autorin bzw. den Autor

Dan R. Lynch is an author and photographer who has written more than 20 field guides, monographs, and kids’ books covering a wide range of topics in the geological sciences. Born and raised on Minnesota’s North Shore of Lake Superior, he learned the nuances of rock and mineral identification firsthand, both on the stony beaches and in his parents’ rock shop, Agate City, in Two Harbors. In his years at the shop, he found that he had a knack for explaining complex topics like rock and mineral formation, putting them in simpler terms for eager novices. Combining this skill with his love of photography and his hands-on background in geology, Dan has prided himself on his series of books in which he guides readers through all aspects of a topic, always starting at the beginning to ensure everyone has a solid foundation for understanding the more technical details that follow. In this way, he hopes to foster an appreciation for the earth beneath our feet, counteract online misinformation, and convey to readers the profound importance of science. Dan lives in Madison, Wisconsin, with his wife and son and works as a classical numismatist and writer.

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Physical aspects and appearance

Turquoise is a mineral known first and foremost for its color—the color turquoise is, in fact, named after the mineral. In mineralogy, color is usually highly variable and is rarely reliable as a diagnostic trait, but that is not so with turquoise. Though the blue-green coloration is not unique to turquoise, the color is so intrinsic to turquoise that it will be an identifying feature when distinguishing it from most other minerals. That is because turquoise’s trademark color is idiochromatic, which means that its color is derived from its essential elements—namely copper—as opposed to many other minerals whose color is often determined by impurities of other elements and minerals trapped in their internal structure. But turquoise’s color is not without variation: Some turquoise is more deeply colored while others are more pale, some are vividly blue, and others will be much more green in hue (a trait caused by the addition of iron to its composition). Coloration can certainly vary greatly from one turquoise deposit to the next, but it can even vary within individual deposits.

Turquoise very rarely forms crystals and instead is almost always found massively. These solid growths consist of tiny intergrown grains of turquoise; the more tightly bonded to each other they are, the higher quality and more colorful the resultant turquoise specimen tends to be. But between the tiny grains are even tinier voids; these pores can become filled with other minerals or substances that can change the physical characteristics of the turquoise. Some specimens with larger pores will have poorer coloration and appear to be softer and more fragile due to lessened cohesion between grains. More porous turquoise also allows more weathering agents—particularly water—to soak into and weaken the turquoise, leaving it chalky and crumbly.

The variability of the cohesion of turquoise grains can also affect the mineral’s trademark color. Turquoise is prone to fading or changing color over time, especially with continued exposure to light and moisture. Porous, low-grade turquoise may appear in vivid shades of blue when mined but often fades to grayer hues shortly after extraction. Conversely, better quality, denser turquoise will retain its vivid coloration much longer. All turquoise, however, weathers relatively quickly when left in the elements, developing a chalky white husk, eventually turning an entire vein or mass of turquoise to clay.

Turquoise masses are usually irregular in shape and fill cavities or cracks in rock, formed there long after the rock itself. As such, the host rock can vary greatly in type and composition. In many cases, the host rock shares nothing of turquoise’s color or traits, causing the turquoise veins to contrast vividly in color, making for very apparent and attractive specimens. Turquoise with even, consistent coloration and no impurities is often considered to be the best and most valuable. But most turquoise contains subtle variations in color and small imperfections, usually inclusions of other minerals or its host rock embedded within it. These veins and masses of other materials are referred to as matrix, a term for the other materials with which turquoise is found embedded and intergrown. A desirable kind of inclusion is known as a “spiderweb” pattern, or “spiderwebbing,” which appears as a network of intertwined veinlets of dark mineral inclusions. Sometimes the spiderwebbing is slight, creating lace-like patterns, but it can also be extensive, with broader “webs” or “nets” appearing to fragment the turquoise, dividing the blue into small cells of color. The finest, best-formed turquoise is that which is solid enough to be cut and polished, while the lowest grade turquoise is usually chalky, crumbly, and nearly impossible to polish without disintegrating.

Turquoise is moderately hard when finely formed, usually able to be scratched by a steel knife or piece of glass but not by a copper or nickel coin. Less cohesive, grainier specimens may seem to be softer, and the chalkiest specimens will appear to be scratched with just a fingernail; this is indicative not of a softer type of turquoise but of the turquoise grains being less compact and more loosely adhered together. Conversely, turquoise that has been naturally indurated, or made harder by other mineral solutions such as silica (quartz), will have a higher hardness.

In nearly all cases, turquoise is opaque, with only very thinly cut or broken pieces showing any amount of translucency. It is also a very brittle mineral, easily broken when struck or dropped. Before polishing, the very finest turquoise will have a luster similar to wax (its surface will reflect light in a manner similar to wax), but the majority of specimens will have a dull luster. After being polished, turquoise will appear much shinier but won’t be as reflective as glass unless it has been naturally indurated or artificially treated.

Chemically, turquoise is a copper-bearing hydrated alkaline aluminum phosphate. Phosphate minerals contain the element phosphorus chemically bonded to oxygen as an essential component, often then bonding with a metal—aluminum is common—and, in the case of turquoise, hydroxide (alkaline) molecules and water. But turquoise also contains some copper atoms bonded to oxygen alongside the aluminum, which gives turquoise its namesake color. It’s this copper content that gives turquoise its “identity” and distinguishes it from other closely related minerals.

Details zur Ausgabe

• Verlag: Adventure Publications, Incorporated
• Erscheinungsdatum: 2025
• Sprache: Englisch
• ISBN 10: 1647553865
• ISBN 13: 9781647553869
• Einband: Tapa blanda
• Anzahl der Seiten: 144
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar