Mineralogical exhibition of Mátra Museum

Minerals of Miocene rhyolites

Minerals of Miocene rhyolites

1. Manganese-oxyde

Manganese-oxyde – MnO Class: Oxides and Hidroxides Crystal system: cubic Characteristic crystal form: aggregate of crystals Hardness: 5,5 Cleavage/Fracture: excellent cleavage/conchooidal fracture Colour: black Streak colour: black Glance: unglazed Locality: Gyöngyössolymos

2. Tridymite (SiO2)

Tridimite – SiO2 Class: Oxides and Hidroxides Crystal system: hexagonal Characteristic crystal form: tabular Hardness: 7 Cleavage/Fracture: no cleavage/conchooidal fracture Colour: white Streak colour: Glance: glassy lustre Locality: Gyöngyössolymos

Opal (SiO2∙nH2O) and Goethite [a-FeO(OH)] 3. Opal (SiO2∙nH2O) and Goethite [a-FeO(OH)]

Opal – SiO2∙nH2O Class: Oxides and Hidroxides Crystal system: amorph Characteristic crystal form: botryoidal, massive, geode Hardness: 5,5 – 6,5 Cleavage/Fracture: no cleavage/conchoidal fracture Colour: colourless, white, red, brown Streak colour: white Glance: glassy, unglazed, earthy, waxy lustre Goethite – -FeO(OH) Crystal system: rhombic Characteristic crystal form: spiky, fibrous Hardness: 5 – 5,5 Cleavage/Fracture: excellent cleavage/hooked fracture Colour: yellow, brown Streak colour: reddish yellow Glance: diamond lustre, semi-metallic lustre Locality: Gyöngyössolymos

4. Opal (SiO2∙nH2O) and Nontronite [(Na, Ca0,5)0,33(Fe3+,Al)2(Si,Al)4O10(OH)2∙nH2O]

Opal – SiO2∙nH2O Class: Oxides and Hidroxides Crystal system: amorph Characteristic crystal form: botryoidal, massive, geode Hardness: 5,5 – 6,5 Cleavage/Fracture: no cleavage/conchoidal fracture Colour: colourless, white, red, brown Streak colour: white Glance: glassy, unglazed, earthy, waxy lustre Nontronite – [(Na,Ca0,5)0,33(Fe3+,Al)2(Si,Al)4O10(OH)2]∙nH2O Class: Silicates Subclass: Fillosilicates Crystal system: monoclinic Characteristic crystal form: earthy, lamellar Hardness: 5 – 5,5 Cleavage/Fracture: excellent cleavage/hooked fracture Colour: green, beownish-green Streak colour: reddish yellow Glance: unglazed Locality: Gyöngyössolymos