Twinned staurolite in thin section
SiO2 varieties
Erythrites
Erythrite (Co3(AsO4)2.8H2O) is a mineral of the Vivianite group and it occurs as a product of the oxidation of Co-Ni-As minerals. The pink color is due to the presence of cobalt.
- Erythrite from Mont Cobalt, Queensland, Australia.
- Erythrite with Skutterudite from Longotoma, Aconcagua, Chile.
Diopsides
Diopsides from Canastra 1, Minas Gerais, Brazil.
Diopside (CaMgSi2O6) is a mineral of the pyroxene group and it's commonly found in metamorphic rocks. It forms a complete solid solution series with hedenbergite (CaFeSi2O6).
Sources:
Klein, C., Hurlbut, C. S., & Dana, J. D. (1999). Manual of mineralogy: (after James D. Dana) (21st ed. rev., pp. 481-482). Wiley.
Lamproite with crustal xenolith (the lighter zone), from Murfreesboro, Arkansas, USA.
Lamproite is a potassic to ultramafic, dark-colored igneous rock group.
Xenoliths are rock fragments carried by igneous rocks. They are older and from a different source than the igneous rocks that contain them.
Olivines from dunites from the Mid-Atlantic Ridge.
Olivine is a mineral group with the general formula (Mg,Fe)2SiO4 and usually found in igneous rocks like gabbro, peridotite, basalt, and dunite. It's abundant in the mantle.
Informations from the 21st edition of the Manual of Mineralogy, by Klein and Hurlbut.
Apophyllite on basalt, from Santa Catarina, Brazil, at the University of São Paulo Institute of Geosciences, Brazil.
Lower Cretaceous Ruffordia goeppertii fossil from the Crato Formation, northeast Brazil. Item of the "Fósseis do Araripe" exposition, from the University of São Paulo Museum of Geosciences, Brazil
A echinoderm fossil and a trilobite fossil from Morocco, at the University of São Paulo Institute of Geosciences, Brazil.
Deactivated lead mine, Iporanga-SP, Brazil. In some of the photos is possible to see calcite precipitating.
Testing a speleothem with hydrochloric acid. The calcium carbonate present in the calcite of the rock reacts with this acid and produces bubbles, carbon dioxide gas, water, and calcium chloride.
Varved deposit from Parque do Varvito, Itú - SP, Brazil
Itaguaré outcrop in Bertioga-SP, Brazil