Quartz-agate
Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/14730981@N08">James Petts</a> from London, England (CC BY-SA 2.0)
Mineral NameQuartz-agate
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Streak ColorWhite
CleavageNone
FractureConchoidal
Specific Gravity2.65
Colorsreddish-orange, yellowish-brown, white
TransparencyTranslucent to opaque
Type LocalityWorldwide
Mineral GroupSilicates
Usesjewelry, ornamental, collector's item
Associated Mineralsquartz
Raritycommon
Description
A nodular specimen, often referred to as a 'potato stone,' displaying an outer layer of reddish-orange and yellowish-brown agate, with an internal cavity lined by small, sparkling white druzy quartz crystals.
Geological Context
Agate forms in cavities within volcanic rocks or ancient lavas, where silica-rich fluids deposit successive layers of cryptocrystalline quartz, often creating banded patterns and sometimes lining geodes with druzy quartz.
