Where is Smoky Quartz with Iron Staining found?
SiO2 (Smoky Quartz) with Fe-oxides/hydroxides
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Open the appSmoky Quartz with Iron Staining occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Smoky Quartz with Iron Staining
Brazil
Known for large quantities of quartz, including smoky quartz, often found in pegmatites and hydrothermal veins, where iron staining is common.
United States (Colorado, Arkansas, North Carolina)
Colorado is famous for its smoky quartz, often associated with pegmatites and granitic intrusions, where iron staining can occur. Arkansas produces clear quartz, but iron-stained varieties are also found. North Carolina also has occurrences in pegmatites.
Switzerland (Alps)
Historically significant source of high-quality smoky quartz, often found in alpine fissures, where iron staining can be present due to weathering processes.
Madagascar
A major source of various quartz varieties, including smoky quartz, where iron staining is frequently observed.
Scotland (Cairngorm Mountains)
The namesake for 'Cairngorm' smoky quartz, often found in granitic rocks, where iron staining can contribute to its appearance.
Collecting tips
- Look for Quartz-Bearing Environments. Focus on areas known for granitic pegmatites, hydrothermal veins, or metamorphic rocks, as these are common hosts for smoky quartz.
- Identify Iron Staining. Look for reddish-brown, orange, or yellowish coatings or patches on smoky-colored quartz crystals. This staining can be superficial and sometimes removed with acid (e.g., oxalic acid), but often it's more integrated.
- Check for Crystal Form. Well-formed hexagonal prisms with rhombohedral terminations are characteristic of quartz. The iron staining might highlight these forms.
- Test Hardness. Quartz is relatively hard (Mohs 7), so it will scratch glass and steel. This helps differentiate it from softer minerals that might have similar coloration.
- Observe Luster and Transparency. Smoky quartz typically has a vitreous luster and is translucent to opaque. The iron staining may reduce transparency in affected areas.
Quick Check
- Color:
- Smoky gray to black with reddish-brown, orange, or yellowish iron staining.
- Luster:
- Vitreous (glassy) on quartz, can be dull or earthy on stained areas.
- Streak:
- White (for quartz), but iron staining may leave a reddish-brown or yellowish streak if rubbed hard enough on a streak plate.
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