Real Quartz vs. Glass: Temperature & Scratch Tests to Identify Clear Quartz

Why Clear Quartz Gets Faked

Clear quartz is the most abundant mineral on earth — and yet it's also one of the most commonly faked in the crystal market. The reason is simple: high-quality, optically clear quartz crystals with good formation are not as common as the raw material, and glass can be made to look nearly identical to clear quartz at a fraction of the cost.

Glass spheres, points, and clusters are sold as "natural crystal quartz" at every price point, from $5 to $500+. Here are four tests to verify you have genuine natural quartz.

Test 1: The Temperature Test — Most Reliable

This is the single most useful test for distinguishing genuine quartz from glass.

How to do it: Hold the stone or sphere against your inner wrist or cheek for 10–15 seconds.

• Genuine quartz: Feels noticeably cool and warms slowly. Natural quartz has low thermal conductivity — it takes significant time to reach body temperature. A large quartz sphere may feel cool for 30 seconds or more.
• Glass: Reaches body temperature much faster. Within a few seconds, glass feels warm or neutral against your skin.

This test works because quartz and glass have different thermal conductivity values. Quartz (SiO₂ crystalline) conducts heat differently than amorphous glass (also SiO₂ but non-crystalline). The crystalline structure of quartz draws heat away from your skin more slowly.

Test 2: The Scratch Test — Hardness

Quartz has a Mohs hardness of 7. Glass has a Mohs hardness of approximately 5.5. This means genuine quartz will scratch glass, but glass will not scratch genuine quartz.

How to do it: Find a piece of standard window glass. Try to scratch the glass surface with the edge or point of your quartz crystal.

• Genuine quartz: Scratches the glass easily, leaving a clear mark.
• Glass imitation: Will not scratch glass, or will leave only a faint surface mark from abrasion.

Important: Perform this test on an inconspicuous area. Also note that some very hard glass (borosilicate) may resist scratching — use standard window glass for best results.

Test 3: The Inclusion Test — Natural vs. Manufactured

Examine the stone under a loupe (10x magnification) or strong magnifying glass in good light.

• Genuine quartz: Contains natural inclusions — tiny fractures (called "veils" or "feathers"), mineral inclusions, growth tubes, or phantoms. These are distributed irregularly throughout the stone. Perfectly clear quartz with zero inclusions does exist but is rare and expensive.
• Glass: May contain perfectly round air bubbles — a definitive sign of manufactured glass. Natural quartz never contains perfectly round bubbles. Glass may also be completely uniform with no internal features, or have swirling flow lines from the manufacturing process.

The presence of perfectly round bubbles is the most reliable single indicator of glass.

Test 4: Weight — Specific Gravity

Quartz has a specific gravity of 2.65. Glass varies but is typically 2.4–2.8. For most common glass types used in crystal imitations, quartz is noticeably heavier.

Compare a suspected piece to a verified quartz piece of similar size. Genuine quartz should feel denser and heavier. This test is most useful when comparing pieces side by side.

What About Synthetic Quartz?

Synthetic (lab-grown) quartz is chemically and crystallographically identical to natural quartz. It passes the temperature, scratch, and weight tests. The inclusion test is the most reliable way to distinguish it: synthetic quartz is typically very clean with few or no natural inclusions, while natural quartz almost always has some natural features. Very high clarity natural quartz exists but commands premium prices.

Quick Reference

Shop Verified Clear Quartz

Every piece in our Clear Quartz collection is genuine natural quartz, verified before purchase. For the complete clear quartz guide, see: The Complete Clear Quartz Guide.