igneous and sedimentary mixture

Quartz / Limestone Gravel

SiO2 (Silicon Dioxide) and CaCO3 (Calcium Carbonate)

Hardness: 7 (Quartz) to 3 (Limestone); Color: White, grey, tan; Luster: Vitreous to earthy; Crystal Structure: Hexagonal (Quartz) / Trigonal (Calcite in limestone); Cleavage: None (Quartz) to Perfect rhombohedral (Calcite).

Hardness: 7 (Quartz) to 3 (Limestone)
Color: White, grey, tan
Luster: Vitreous to earthy

Identified April 8, 2026More igneous and sedimentary mixture →

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Physical properties

Formation & geological history

The white specimen in the center is likely quartz, formed in hydrothermal veins or igneous intrusions. The surrounding gravel is limestone, formed by the accumulation of shells and coral in shallow marine environments over millions of years.

Uses & applications

Quartz is used in electronics and glass-making. Limestone gravel (crushed stone) is primarily used in road construction, concrete production, and as a base material for driveways.

Geological facts

Quartz is one of the most abundant minerals in the Earth's crust and is highly resistant to chemical weathering. Limestone accounts for about 10% of the total volume of all sedimentary rocks.

Field identification & locations

Identify Quartz by its ability to scratch glass and lack of cleavage. Identify Limestone with an acid test (it will fizz when in contact with diluted hydrochloric acid). Commonly found in quarries and as landscaping material in suburbs.

Other igneous and sedimentary mixture specimens

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Chalcedony (Agate/Quartz variety)

Cryptocrystalline Quartz (SiO2)

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Dalmatian Jasper

Dalmatian Stone (a microcrystalline quartz and feldspar rock with arfvedsonite)

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Dalmatian Stone (commonly Dyed)

Dalmatian Jasper (Peralkaline igneous rock)

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Granite Sand (Decomposed Granite)

Grus / Quartz-Feldspar Detritus

sedimentary

Dalmatian Stone

Dalmatian Jasper (a misnomer) / Perthitic Igneous Rock

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Limonite / Ironstone Nodule

Limonite (Hydrated iron(III) oxide-hydroxide), FeO(OH)·nH2O

mineral