The purple specimen is a mineral (Amethyst); the white specimen is a sedimentary rock (Limestone or Marble).
Amethyst and Limestone
Amethyst (SiO2 - Silicon Dioxide) and Limestone (CaCO3 - Calcium Carbonate)
Amethyst: Hardness 7 (Mohs), purple color, vitreous luster, hexagonal crystal system. Limestone: Hardness 3 (Mohs), white/grey color, dull/earthy luster, reacts with HCl acid.
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Physical properties
Amethyst: Hardness 7 (Mohs), purple color, vitreous luster, hexagonal crystal system. Limestone: Hardness 3 (Mohs), white/grey color, dull/earthy luster, reacts with HCl acid.
Formation & geological history
Amethyst forms in volcanic geodes through hydrothermal activity. Limestone forms from the accumulation of marine skeletal fragments or the precipitation of calcium carbonate in shallow marine environments.
Uses & applications
Amethyst is primarily used for jewelry and metaphysical collecting. Limestone is used in construction as an aggregate, cement production, and as an industrial soil conditioner.
Geological facts
Amethyst was once considered one of the 'Cardinal Gems' along with diamond and ruby until large deposits were found in Brazil. Limestone is the primary component of the Great Pyramids and many Gothic cathedrals.
Field identification & locations
Identify Amethyst by its quartz crystal structure and violet hue (caused by irradiation of iron impurities). Identify Limestone/Marble by its softness compared to steel and its effervescence when exposed to weak acid.
More like this
Other the purple specimen is a mineral (amethyst); the white specimen is a sedimentary rock (limestone or marble). specimens
Marble
Recrystallized Calcite (CaCO3) or Dolomite (CaMg(CO3)2)
metamorphic
Marble (Carrara style)
Recrystallized Calcite-rich Metamorphic Rock (CaCO3)
metamorphic
Quartz on Matrix
Silicon Dioxide (SiO2)
mineral
Marble
Metamorphosed Limestone (calcite formulation CaCO3)
metamorphic
Quartz Geode (partially formed)
Silicon Dioxide (SiO2)
mineral
White Marble
Recrystallized Calcite (CaCO3)
metamorphic