- Asked 2/29
- 2081 Kartik (new course) · 2 marks
- 2076 Chaitra · 0.5 marks
Silicate versus carbonate minerals in the field
Short answer
Apply dilute HCl: carboantes effervesce (calcite vigorously, dolomite when powdered), while silicates do not react. Carboantes are soft (hardness 3-4) with rhombohedral cleavage; silicates are harder (5.5-7, except micas 2-3) and lack such cleavage. A knife scratch and acid test quickly distinguish them.
How do you identify (differentiate) silicate minerals and carbonate minerals in the field?
Silicate and carbonate minerals can be distinguished in the field by a few simple tests.
| Test | Silicate minerals | Carbonate minerals |
|---|---|---|
| Dilute HCl | No reaction | Effervescence (calcite fizzes strongly; dolomite only when powdered) |
| Hardness | Mostly 5.5-7 (quartz and feldspar scratch glass); micas are soft (2-3) | Soft, 3-4 (scratched by knife) |
| Cleavage | Varies (mica one, feldspar two, quartz none) | Perfect rhombohedral cleavage (3 directions) |
| Specific gravity | 2.5-3.5 | About 2.7-2.9 |
| Lustre | Vitreous, pearly | Vitreous to dull |
| Examples | Quartz, feldspar, mica, olivine | Calcite, dolomite |
The fastest field test is the acid test with a drop of dilute HCl, together with a knife scratch.
✓ Answer checked by Claude Opus 5.5 (high effort)
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