Where is Basalt with secondary minerals found?
Basalt with secondary minerals (possibly epidote and quartz)
Got a photo? Identify rocks instantly with the Rockby app
Open the appBasalt with secondary minerals 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 Basalt with secondary minerals
Deccan Traps, India
Extensive flood basalts with abundant zeolites, calcite, and other secondary minerals filling amygdales.
Columbia River Basalt Group, USA
Large igneous province with altered basalts containing various secondary minerals.
Mid-ocean ridges and ophiolite complexes worldwide
Sites of active hydrothermal alteration of oceanic crust, leading to epidote, chlorite, and quartz formation.
Iceland
Active volcanic island with basalts undergoing ongoing hydrothermal alteration and secondary mineralization.
Lake Superior Region, USA/Canada
Keweenawan basalts are famous for copper mineralization associated with zeolites, epidote, and quartz.
Collecting tips
- Look for Vesicular Basalts. Secondary mineralization is most prominent in vesicular basalts, where gas bubbles provided open spaces for mineral precipitation. Look for rocks with visible holes or cavities.
- Examine Outcrop Surfaces. Weathered surfaces may highlight the different colors and textures of secondary minerals compared to the darker basalt matrix. Fresh breaks can reveal crystal forms.
- Check for Veins and Fractures. Hydrothermal fluids often travel along fractures, leading to the formation of mineral veins that cut through the basalt.
- Associated with Hydrothermal Activity. Areas with past or present geothermal activity, hot springs, or evidence of fluid flow are good places to search.
- Use a Hand Lens. A hand lens (10x magnification) is essential to identify the specific secondary minerals, their crystal habits, and their relationship to the basalt matrix.
Quick Check
- Color:
- Dark gray to black matrix with green (epidote, chlorite), white/colorless (quartz, calcite, zeolites), or other colored infillings.
- Luster:
- Dull to sub-vitreous for basalt; vitreous, pearly, or dull for secondary minerals.
- Streak:
- White to grayish-white for the basalt matrix. Individual secondary minerals will have their characteristic streak (e.g., white for quartz and calcite, greenish-white for epidote).
Explore Basalt with secondary minerals
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.