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Ametista do Sul (São Gabriel), Rio Grande do Sul, Brazili
Regional Level Types
Ametista do Sul (São Gabriel)- not defined -
Rio Grande do Sul- not defined -

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"The world's amethyst capital".
The genesis of amethyst geodes in basalts (Serra Geral Formation) at Ametista do Sul, Brazil, is considered as a two-stage process with an early magmatic protogeode formation and a late, low temperature infill of the cavity.

Originally named São Gabriel, renamed Ametista do Sul back in the 1980s.

The municipality of Ametista do Sul and the little town with the same name are undoubtedly the world's capital of amethyst, at least in terms of current production. At any one time there are probably a substantially greater tonnage of amethyst in Soledade than in Ametista because that is the commercial town where most of the amethyst and agate and other stones are sold. The production from the mines at Ametista do Sul does not hang around the town or the mines very long before being sold and hauled off to Soledade. The town used to be called Sao Gabriel and the quickest way to get there from Soledade was to take a ferry across the river and of course the roads were not paved.

"The amethyst mines are just on the edge of town, in a little valley where they can be seen as a line of horizontal black holes near the valley floor. The amethyst is mined from a flat laying layer basalt that is rich in amethyst and the mining method is simply to punch tunnels into the basalt parallel to each other and mine out the amethyst geodes that are encountered in the mining process." [Rock Currier 2011]

Regions containing this locality

South America PlateTectonic Plate
South AmericaContinent

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

6 valid minerals. 1 erroneous literature entry.

Detailed Mineral List:

Formula: CaSO4
Habit: Tabular
Colour: white to pink
Description: All the "anhydrite" blades from this locality are hollow paper thin quartz epimorphs with all the anhydrite gone.
Reference: Don Windeler collection
Formula: CaCO3
Reference: Mossmann, D. J. et al. (2009): "Skunk calcite". Mineral Paragenesis in an amethyst geode from Ametista, Rio Grande do Sul, Brazil. Mineralogical Record. 40:121-125
Formula: K(Mg,Fe2+)Fe3+(Si4O10)(OH)2
Formula: α-Fe3+O(OH)
Reference: Mossmann, D. J. et al. (2009): "Skunk calcite". Mineral Paragenesis in an amethyst geode from Ametista, Rio Grande do Sul, Brazil. Mineralogical Record. 40:121-125
Formula: CaSO4 · 2H2O
Lepidocrocite ?
Formula: γ-Fe3+O(OH)
Colour: yellow
Description: thin yellow patina on calcite
Reference: Mossmann, D. J. et al. (2009): "Skunk calcite". Mineral Paragenesis in an amethyst geode from Ametista, Rio Grande do Sul, Brazil. Mineralogical Record. 40:121-125
Formula: SiO2
Quartz var: Agate
Reference: Mineralogical Record (2009) 40:121-125
Quartz var: Amethyst
Formula: SiO2
Reference: Mineralium Deposita (2003) 38 (8), 1009-1025; Mineralogical Record (2009) 40:121-125
Quartz var: Chalcedony
Formula: SiO2
Reference: Mineralogical Record (2009) 40:121-125

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Lepidocrocite ?4.FE.15γ-Fe3+O(OH)
var: Agate4.DA.05SiO2
var: Amethyst4.DA.05SiO2
var: Chalcedony4.DA.05SiO2
Group 5 - Nitrates and Carbonates
Group 7 - Sulphates, Chromates, Molybdates and Tungstates
Anhydrite ?7.AD.30CaSO4
Gypsum7.CD.40CaSO4 · 2H2O
Group 9 - Silicates

List of minerals arranged by Dana 8th Edition classification

Lepidocrocite ?γ-Fe3+O(OH)
Anhydrite ?
Gypsum29.6.3.1CaSO4 · 2H2O
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Unclassified Minerals, Mixtures, etc.
var: Agate-SiO2
var: Amethyst-SiO2
var: Chalcedony-SiO2

List of minerals for each chemical element

H GypsumCaSO4 · 2H2O
H CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
H Goethiteα-Fe3+O(OH)
H Lepidocrociteγ-Fe3+O(OH)
C CalciteCaCO3
O Quartz (var: Amethyst)SiO2
O GypsumCaSO4 · 2H2O
O CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
O CalciteCaCO3
O Goethiteα-Fe3+O(OH)
O QuartzSiO2
O Quartz (var: Chalcedony)SiO2
O Lepidocrociteγ-Fe3+O(OH)
O AnhydriteCaSO4
Mg CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
Si Quartz (var: Amethyst)SiO2
Si CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
Si QuartzSiO2
Si Quartz (var: Chalcedony)SiO2
S GypsumCaSO4 · 2H2O
S AnhydriteCaSO4
K CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
Ca GypsumCaSO4 · 2H2O
Ca CalciteCaCO3
Ca AnhydriteCaSO4
Fe CeladoniteK(Mg,Fe2+)Fe3+(Si4O10)(OH)2
Fe Goethiteα-Fe3+O(OH)
Fe Lepidocrociteγ-Fe3+O(OH)

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Cretaceous - Jurassic
66 - 201.3 Ma

ID: 3185981
Mesozoic volcanic rocks

Age: Mesozoic (66 - 201.3 Ma)

Stratigraphic Name: Parana Flood Basalt

Lithology: Flood basalt(s); mafic volcanic rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Early Cretaceous
100.5 - 145 Ma

ID: 2320219
Paranapanema Fácies

Age: Early Cretaceous (100.5 - 145 Ma)

Lithology: Andesite, basalt

Reference: Geological Survey of Brazil. State Geological Maps of Brazil. CPRM - Geobank. [43]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License


Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Gilg, H.A., Morteani, G., Kostitsyn, Y., Preinfalk, C., Gatter, I., Strieder, A.J. (2003) Genesis of amethyst geodes in basaltic rocks of the Serra Geral Formation (Ametista do Sul, Rio Grande do Sul, Brazil): a fluid inclusion, REE, oxygen, carbon, and Sr isotope study on basalt, quartz, and calcite. Mineralium Deposita: 38 (8): 1009-1025.
Mossmann, D. J., Ehrman, J. M., Brüning, R., Semple, L., Groat, L.A. (2009) "Skunk calcite". Mineral Paragenesis in an amethyst geode from Ametista, Rio Grande do Sul, Brazil. Mineralogical Record 40: 121-125.
Rosenstengel, L.M., Hartmann, L.A. (2012) Geochemical stratigraphy of lavas and fault-block structures in the Ametista do Sul geode mining district, Paraná volcanic province, southern Brazil. Ore Geology Reviews: 48: 332-348.

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