Pink Chalcedony Nodule from Arizona DX2690

Chalcedony Nodule
Approx. Dimensions: 4.5 x 3.5 x 2 inches
Approx. Weight: 343 grams
Locality: Green Fire Prospect, Cochise County, Arizona, USA

Includes the acrylic 3-prong stand as shown in the photos.

This unique formation of chalcedony from Arizona has a lovely pale pink color. It will fluoresce green under long and short wave UV lights (shown in the last two photos respectively), possibly due to trace amounts of uranium present in the chalcedony.

Chalcedony is a microcrystalline form of silica, which is the primary component of quartz. It is a type of cryptocrystalline quartz, meaning that its crystals are so small that they are not easily distinguishable even under a microscope. Chalcedony typically has a waxy or glassy appearance and is known for its various colors and patterns.

The primary reason chalcedony forms differently than quartz crystals lies in the rate of crystal growth and the presence of impurities. Both chalcedony and quartz are made up of silicon dioxide (SiO2) molecules arranged in a repeating pattern, but the specific arrangement and growth conditions lead to the differences in their appearance and formation.

Quartz crystals usually form in open spaces with sufficient room for individual molecules to arrange themselves into well-defined, larger crystals. This occurs under conditions of slow cooling and low pressure, allowing the silicon dioxide molecules to arrange themselves into a more ordered, geometric structure. These larger crystals often have visible facets and well-defined crystal shapes.

Chalcedony, on the other hand, forms in a more compact environment with limited space for crystal growth. It typically forms in cavities, fractures, or vesicles within rocks. The restricted space prevents the silicon dioxide molecules from arranging themselves into large, distinct crystals. Instead, they form aggregates of tiny crystals that are intertwined, giving chalcedony its microcrystalline texture. This texture is responsible for the smooth and often translucent appearance of chalcedony.

Impurities also play a role in the formation of chalcedony. Trace elements or other minerals present in the environment during chalcedony's formation can influence its color and pattern. For instance, iron oxide impurities can lead to the formation of red chalcedony (carnelian), while manganese impurities can result in lavender chalcedony (amethystine quartz). These impurities contribute to the diverse array of colors observed in chalcedony.

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