metamorphic
Orange Quartzita (Calcite-stained Quarzite)
Metamorphic Silicon Dioxide (SiO2) with iron/calcium inclusions
Hardness: 7 (Mohs scale), Color: Honey-yellow to pale orange, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Honey-yellow to pale orange, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone (orthoquartzite) under intense heat and pressure, typically during tectonic mountain-building events. The yellowish hue is often due to iron oxide staining or calcite impurities during the recrystallization process.
Uses & applications
Used in landscaping, construction as crushed stone, and sometimes as a decorative tumble stone or lapidary material for jewelry. High-purity quartzite is used to produce silicon for industrial applications.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the resistant caps of ridges and mountains. In its pure form, it is white, but impurities can turn it yellow, orange, green, or red.
Field identification & locations
Identify by its ability to scratch glass and its lack of reaction to acid (unlike calcite). It lacks the rhythmic banding seen in agates. Commonly found in riverbeds or glacial tills across North America and Europe.
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