Quartz (trigonal, low-temperature α-quartz) is the most important polymorph of the silica
(SiO2) group and one of the purest minerals in the Earth crust. The mineralogy and mineral …

Agate—a spectacular form of SiO2 and a famous gemstone—is commonly characterized as
banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated …

The most widely used geochronometer for dating geological events is the U–Pb isotope
system used on zircon crystals. However, in silica-undersaturated ultramafic and alkaline …

Genetic models for the formation of uranium deposits almost invariably invoke the reduction
of U (VI) to U (IV) as the deposition mechanism. However, the questions of when and how …

We analyzed hydrothermal silicification along the Afonso Bezerra strike-slip fault system in
the Potiguar Basin, equatorial margin of Brazil, to assess the role of Si-rich fluids in fault …

An organic-rich laminated chert (silicilyte) consisting of up to 90% microcrystalline quartz
that formed at the Precambrian–Cambrian boundary acts as a light-oil reservoir in the …

Agate and carnelian beads, imported from South Asia, were widely exchanged in Southeast
Asia during the Iron Age period (500 BCE–500 CE). Recent studies have identified changes …

Abstract The Bakoshi-Kundila Au deposit is located in the Nigerian Shield in West Africa. In
this deposit, Au-bearing pyrite contains inclusions of Au-rich hydrothermal quartz. Whether …

This review covers the last 250 years of major scientific contributions on the genesis of
agates found in basic igneous host rocks. From 1770 to 1955, the genesis question was …

In this work, we studied the hydrothermal agates from the Neogene–Quaternary volcanic
district of Allumiere-Tolfa, north-west of Rome (Latium, Italy) using a combination of micro …