RocksdayApophyllite vs Quartz
How to tell them apart
A sparkling silicate from cavities in basalt, forming blocky square crystals with pyramid tips.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
The second most abundant mineral in Earth's crust. Clear crystals grow as six-sided prisms capped by a pointed termination, and quartz shows up as grains in sand, granite and countless other rocks.
Photo: Didier Descouens, CC BY-SA 4.0
Quick tests
- Scratch glass: Quartz scratches glass (Mohs 7); Apophyllite can't (Mohs 4.5–5).
Key differences
- Quartz is harder and its crystals are hexagonal.
Side by side
| Property | Apophyllite | Quartz |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 4.5–5 | 7 |
| Luster | Vitreous to pearly | Vitreous |
| Streak | White | White |
| Colors | Clear, White, Green | Clear, White, Gray |
| Crystal system | Tetragonal | Trigonal |
| Specific gravity | 2.3–2.4 | 2.65 |
| Formula | KCa₄Si₈O₂₀(F,OH)·8H₂O | SiO₂ |
| Found in | Pune, India; Nashik, India | Hot Springs, Arkansas; Minas Gerais, Brazil |
Properties that are the same for both are grayed out.
How to identify apophyllite
- Clear or mint-green square prisms or pyramids.
- Pearly shine on the flat top faces.
- Softer than quartz — a knife scratches it.
Crystal system: Tetragonal
Full Apophyllite guide →How to identify quartz
- Scratches glass easily and can't be scratched by a steel knife.
- Six-sided prisms with pointed ends when it forms crystals.
- Breaks with curved, shell-like (conchoidal) fractures — no flat cleavage planes.
- Does not fizz in vinegar or dilute acid.
Crystal system: Trigonal
Full Quartz guide →More comparisons
Could you tell them apart from a blurry close-up?
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