2.7" Stilbite Crystals on Sparkling Quartz Chalcedony - India
This is a beautiful, 2.7" wide, sparkling chalcedony formation with stilbite crystals, collected from Maharashtra, India. There is a natural healed fracture through this specimen.
Stilbite is a tectosilicate mineral of the zeolite group that is commonly found in zeolite deposits. Crystals often form flowery, bowtie or hourglass shaped structures and come in a variety of colors. Some of the most beautiful colorations are the pink or peach tints.
Chalcedony is any microcrystalline variety of silica composed of very fine intergrowths of quartz and moganite. Microcrystalline meaning the crystals are microscopic and cannot be observed by the naked eye. Both quartz and moganite have the same chemical formula SiO2 (silicon dioxide) but different crystal structures. When free from impurities, chalcedony is colorless and transparent. Dependent on impurities present during formation, chalcedony can form in a wide variety of colors including red, yellow, green, blue, purple, grey, white and numerous color hues in between. Chalcedony is quite hard, being a 7 on the Mohs Hardness Scale, which makes sense considering quartz is the benchmark mineral for a 7.
Silicon Dioxide, also known as SiO2 or Quartz, is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich, hot watery solutions called hydrothermal environments, at temperatures between 100°C and 450°C, and usually under very high pressure. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountains forming, and can be hundreds of millions of years old.