Clear Quartz Identification Guide
A practical field guide to identifying colorless rock crystal quartz by its hexagonal habit, hardness, and how to separate it from glass, calcite, and topaz.
Read the full Clear Quartz encyclopedia entry →
What Clear Quartz Looks Like
Clear quartz (rock crystal) is colorless and transparent crystalline silica (SiO₂). It commonly grows as six-sided (hexagonal) prisms terminated by six-faced pyramidal points, often with horizontal striations across the prism faces. Luster is glassy (vitreous), and good crystals are water-clear, though many show internal veils, fractures, or milky bases. It can also occur massive or as anhedral chunks without faces.
Step-by-Step Field ID Checklist
- Look for crystal form. Search for six-sided prisms ending in a pointed termination — a near-instant clue.
- Check for striations. Run your eye across prism faces; horizontal growth striations are characteristic.
- Test transparency and color. True rock crystal is colorless and transparent, not milky throughout.
- Do a hardness test. It scratches glass and steel easily and is not scratched by a knife.
- Check the break. Quartz has no cleavage; broken surfaces are conchoidal and glassy.
- Feel temperature. Quartz feels distinctly cold to the touch, unlike glass.
Key Diagnostic Tests
- Hardness: 7. It scratches glass (5.5) and steel; nothing common in the field scratches it except topaz, corundum, or diamond.
- Streak: White.
- Cleavage/fracture: No cleavage; conchoidal fracture.
- Density: 2.65 g/cm³.
- No acid reaction, non-magnetic.
- Optics: Single point quartz shows no strong double refraction; calcite, by contrast, doubles images.
Common Look-Alikes and How to Tell Them Apart
- Glass: Glass is softer (5–5.5), so quartz scratches it but not vice versa. Glass shows mold seams, bubbles, and lacks natural crystal faces. Glass feels warmer.
- Calcite (Iceland spar): Calcite is much softer (3), fizzes in dilute acid, has perfect rhombic cleavage, and produces a doubled image when you look through it. Quartz does none of these.
- Topaz: Topaz is harder (8) and has one perfect basal cleavage; quartz has none. Topaz crystals are often more elongated with different terminations.
- Selenite gypsum: Very soft (2), can be scratched with a fingernail; quartz cannot.
- Clear obsidian: Amorphous glass, hardness 5–5.5, conchoidal fracture only, no crystal faces.
Where It Is Found
Clear quartz is one of Earth's most abundant minerals, found in pegmatites, hydrothermal veins, vugs, and geodes worldwide. Famous sources include Arkansas (Hot Springs/Mount Ida), Brazil, Madagascar, the Alps, and Herkimer County, New York (the doubly terminated "Herkimer diamonds"). Look in quartz veins, granite cavities, and stream gravels.
Frequently asked questions
How can you tell if clear quartz is real?
Real clear quartz has hardness 7 (scratches glass and steel), no cleavage, conchoidal fracture, feels cold, and often shows six-sided prisms with striated faces ending in a point. Glass imitations are softer and warmer.
What is the difference between clear quartz and glass?
Quartz is harder (7 vs glass's 5.5), so it scratches glass. Quartz feels cold, grows in natural hexagonal crystals, and lacks bubbles or mold seams; glass is warmer and often has bubbles.
Clear quartz vs calcite — how do I tell them apart?
Calcite is soft (3), fizzes in vinegar or acid, has perfect rhombic cleavage, and doubles images seen through it. Clear quartz is hard (7), does not fizz, and has no cleavage.
What does clear quartz look like in nature?
It typically forms colorless, transparent six-sided prisms with horizontal striations, capped by a six-faced pyramid point, often clustered in veins, vugs, or geodes.
Is clear quartz the same as rock crystal?
Yes. "Rock crystal" is the traditional name for colorless transparent quartz, the same material sold as clear quartz.
Clear Quartz identified by the community
Recent Clear Quartz specimens identified with Rock Identifier.
