metamorphic
Slate with Quartz
Low-grade Metamorphic Slate with SiO2 inclusions
Hardness: 3-5.5 (slate), 7 (quartz); Color: Grey, black, rusty brown with white/pink quartz; Luster: Dull to sub-vitreous; Crystal structure: Foliated (slate), Trigonal (quartz); Cleavage: Perfect slaty cleavage.
- Hardness
- 3-5
- Color
- Grey, black, rusty brown with white/pink quartz
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 3-5.5 (slate), 7 (quartz); Color: Grey, black, rusty brown with white/pink quartz; Luster: Dull to sub-vitreous; Crystal structure: Foliated (slate), Trigonal (quartz); Cleavage: Perfect slaty cleavage.
Formation & geological history
Formed through low-grade regional metamorphism of shale or mudstone. Quartz veins often form later through hydrothermal activity. Typical of Paleozoic or older mountain-building events.
Uses & applications
Slate is used for roofing, flooring, and billiard tables. Quartz is used in glass making and electronics. Collected primarily for educational purposes or landscaping.
Geological facts
Slate is unique for its ability to be split into thin, flat sheets. The reddish hue on some of these rocks is likely iron oxide staining from the weathering of pyrite or other iron-bearing minerals.
Field identification & locations
Identify by its 'slaty' cleavage (splitting along flat planes) and the presence of hard, non-cleaving quartz veins. Commonly found in riverbeds within metamorphic belts.
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