4.1" Las Choyas "Coconut" Geode with Smoky Quartz & Calcite - Mexico

 
 
This is a beautiful "coconut geode" from Chihuahua, Mexico. It's lined with smoky quartz crystals and has calcite crystals peppered throughout the geode. Under magnification, acicular crystals can be found as both inclusions and as individual crystals throughout the geode. Both halves are included and come with acrylic display stands.

Geodes are rounded, hollow voids in rocks filled with crystals and other minerals. They are typically formed when air bubbles inside of volcanic rock form hollow cavities. Over time, as mineral-rich water seeps into the rock it beings to deposit tiny crystals on the sides the hollow cavity. After millions of years, the flow of water gradually builds crystals inside the empty space.

Las Choyas geodes, often referred to as coconut geodes are mined from 100 to 200 feet below the surface near Chihuahua, Mexico. Shafts are drilled down to the geode bearing white clay, and then tunnels are dug horizontally to extract the geodes.

The geodes typically range from about 2-6 inches in diameter and can contain a variety of minerals and crystals. Most hollow geodes contain a variety of quartz ranging from clear quartz to smoky quartz to more rarely amethyst. Many secondary minerals such a goethite, hematite, mordenite, calcite and galena may also be present in some geodes.

Smoky quartz is a grey-brown to black variety of quartz. This common name is derived from from the appearance of smoke within the quartz crystal. Dependent on the location and the chemicals present during formation, smoky quartz can appear opaque black, however it’s typically translucent to some extent. It’s believed that the quartz gains this color from a combination of natural irradiation and aluminum impurities.

Calcite, CaCO3, is a carbonate mineral and the most stable polymorph of calcium carbonate. The other polymorphs are the minerals aragonite and vaterite. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals. However, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, and prisms. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form.
DETAILS
SPECIES
Quartz var. Smoky & Calcite
LOCATION
Chihuahua, Mexico
SIZE
4.1" wide
CATEGORY
SUB CATEGORY
ITEM
#145857