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Crystal Structure
Tectosilicate; trigonal space group P3121 or P3221 (enantiomorph).
External databases provide CIF (Crystallographic Information File) downloads + interactive 3D viewers. AMCSD: American Mineralogist Crystal Structure Database (free, RRUFF-hosted). COD: open community-curated database.
Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| O Oxygen | 53.26% | |
| Si Silicon | 46.74% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
Reference Resources
- Comprehensive species record + 60+ localities
- Reference spectra
- Gemological standards reference
IMA Abbreviation (Whitney-Evans 2010)
Qz
→ Quartz
Petrology, thin sections, P-T diagrams
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/kwɔːrts/
↔ kwartz
one syllable (German)
UV Fluorescence
SW (254 nm)
—
none
LW (365 nm)
—
none
Pure quartz inert.
SW = shortwave (germicidal lamp). LW = longwave (blacklight). Response varies with locality, trace impurities, and treatment.
Pseudomorph Relationships
Replaces — this mineral is often a pseudomorph after:
← Aragonite replacement
Aragonite (orthorhombic CaCO₃) inverts to quartz with shape preservation. Pseudohexagonal quartz from this process.
Spain (Aragón).
← Fluorite replacement
Hexagonal quartz crystals filling cubic fluorite voids — "Cumberland diamonds".
Cumbria, UK.
← Calcite replacement
Cone-shaped quartz pseudomorphs after scalenohedral calcite — sometimes called "babingtonite".
Cornwall; Bohemia.
A pseudomorph (Greek "false form") is a mineral with the external shape of another species — the chemistry has changed but the crystal habit is inherited. › Full catalogue
Tenacity
Behavior:
brittle
Under stress:
Conchoidal fracture under blow
Hard but brittle — sharp hammer-strike produces conchoidal flakes.
Luster
vitreous
Glassy luster — reference for the term.
Notable localities (coordinates)
- Mt. Ida — Arkansas, USA34.5500, -93.6300 › OpenStreetMap
- Herkimer County — New York, USA43.0300, -74.9700 › OpenStreetMap
All localities and full GeoJSON available at /wp-json/mmb/v1/localities-geo
Diaphaneity (Transparency)
transparent
Rock crystal is highly transparent; varieties vary widely.
Type Locality
(ancient — German "quarz") — Worldwide
Source: Mathesius 1553
Magnetism
Category:
diamagnetic
Test result:
Slight repulsion
SiO₂; pure quartz is diamagnetic.
Test with rare-earth magnet (N42 or N52 neodymium). Suspend specimen on thread for sensitive paramagnetic detection. Diamagnetic minerals are weakly repelled (visible only with strong magnets like bismuth).
Diagnostic Field Tests
Hardness→ Mohs 7 — scratches glass and steel
Reference point for the hardness scale.
HCl test→ No reaction
No fizz — distinguishes from calcite of similar habit.
Cleavage→ None — conchoidal fracture
Distinguishes from feldspar (which has cleavage).
⚠ Use dilute HCl (~10%) only on inconspicuous spots; rinse promptly. Smell-tests should be brief and ventilated. Taste-test ONLY halite/sylvite — never lead, arsenic, or sulfur minerals.
Specific Gravity
2.65
g/cm³
light
Standard reference for low-SG transparent gem material.
For comparison: water = 1.00, glass ≈ 2.5, quartz = 2.65, corundum ≈ 4.00, galena ≈ 7.50, gold ≈ 19.3.
Synthetics & Imitations
Lab-grown methods
Hydrothermal 1900 · Spezia
Industrial-scale since 1950s for electronics. Lab citrine, amethyst, and rose quartz all readily synthesized.
Common imitations
Glass
Singly refractive, conchoidal fracture, gas bubbles.
Geological Setting
Environment:
multiple
Host rock:
granite, pegmatite, hydrothermal vein, sedimentary
Companions:
The most ubiquitous mineral — present in virtually every silicic igneous, metamorphic, and many sedimentary environments.
Treatments & Enhancements
Irradiationoccasionalstable· detection: hard
Used for smoky quartz from natural colorless quartz, and to deepen amethyst color.
As a buyer: request written disclosure of treatments and confirm whether the price reflects treated or untreated material.
Characteristic Inclusions
Rutile needlessolid★ diagnostic
Golden, red, or copper-colored TiO₂ needles ("Venus hair", "Cupid's darts"). Often radiate from a single point.
Tourmaline crystalssolid
Black schorl or green elbaite prisms suspended inside ("tourmalinated quartz").
Chlorite phantomssolid
Green chlorite distributed along earlier growth faces, creating ghost crystal outlines.
Two-phase inclusionstwo-phase
Negative crystal cavities containing liquid + vapor bubble that moves when warmed.
★ Diagnostic inclusions are characteristic enough to help identify origin or species under 10× loupe.
Twinning Laws
Japan lawcontact
Two crystals joined at 84°33′. Striking flat "V" shape; rare and highly collectible.
Dauphiné lawpenetration
Common 60° rotation around c-axis. Usually invisible in habit; affects optical/piezoelectric behavior.
Brazil lawpenetration
60° rotation about a-axis. Combines right- and left-handed quartz. Visible via etch figures.
Care notesRobust — water + soft brush + non-ionic detergent fine. Ultrasonic OK for solid pieces, NOT for phantoms or twinned. Full cleaning guide →
Formation eraUbiquitous across geological time; Cornish hydrothermal Variscan ~290 Ma.
★★★★★5 / 5 based on 17 customer reviews across 50 specimens
Cleavage & Fracture
Cleavage:
none —
Fracture:
conchoidal
No cleavage — quartz fractures conchoidally (shell-like).
Market availability: Common
Widely available in most dealer stocks. Specimens span all price tiers.
Collector tier: Cabinet Classic
World-class display species — sought after for cabinet collections, well-documented localities, frequent show-piece pieces.
PolymorphsShares the formula
SiO2 with: Tridymite · Cristobalite · Coesite · Stishovite — same chemistry, different crystal structure.Named varieties — color spectrum
Mohs 7
Vickers (~) 1400 HV
Knoop (~) 1100 HK
Nickel–Strunz
4.DA.05Dana
75.01.03.01Geological setting
PegmatiteHydrothermal
Diagnostic properties
PiezoelectricPyroelectric
Element composition by mass
Formula: SiO₂ · molar mass: 60.08 g/mol
| O | 53.26% | |
| Si | 46.74% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
GroupQuartz Group (silica)
Mohs Hardness
7
Quartz sits at 7 on the Mohs scale — harder than glass; scratches steel.
Colors:
Streak
White
White
Crystal system
Trigonal
Trigonal
Pronunciation/kwɔːrts/
Type localityCornwall, England (classical)
✓ I have this★ WishlistView my collection →
Discovery Known since antiquity
SilicatesSilicates — Tectosilicates
TL;DR · 1 min read
Quartz is the most abundant mineral exposed at Earth's surface — and despite its commonness, it produces some of the finest collector specimens in mineralogy. From Himalayan ice-clear crystals to the deep purple amethysts of Vera Cruz, quartz is the species every collector returns to.
Text size:AAA
Quartz is the most abundant mineral exposed at Earth's surface — and despite its commonness, it produces some of the finest collector specimens in mineralogy. From Himalayan ice-clear crystals to the deep purple amethysts of Vera Cruz, quartz is the species every collector returns to.
Notable Varieties #
- Amethyst (purple, Fe-bearing)
- Citrine (yellow, heat- or radiation-induced)
- Smoky Quartz (brown to black, radiation damage)
- Rose Quartz (pink, Ti/Fe inclusions)
- Rock Crystal (colorless)
- Morion (opaque black)
The Chinese Angle #
Tibetan and Sichuan high-altitude pegmatites produce extraordinarily clear quartz crystals with fine terminations and minimal inclusions. The Yaogangxian district yields milky quartz matrix material for fluorite specimens, while Hunan produces some of the world's best fenster (window) quartz.
Test at home — what scratches what
Will scratch your specimen:
🪨 Topaz scratch test (Mohs 8) · 💎 Corundum (sapphire/ruby) (Mohs 9) · 💠 Diamond (Mohs 10)
🪨 Topaz scratch test (Mohs 8) · 💎 Corundum (sapphire/ruby) (Mohs 9) · 💠 Diamond (Mohs 10)
Your specimen will scratch:
👆 Talc dust (Mohs 1) · 💅 Fingernail (Mohs 2.5) · 🪙 Copper coin (US penny) (Mohs 3.5) · 🔪 Steel pocket knife (soft steel) (Mohs 5) · 🥃 Glass plate (Mohs 5.5) · 🔧 Steel file / hardened steel (Mohs 6.5)
👆 Talc dust (Mohs 1) · 💅 Fingernail (Mohs 2.5) · 🪙 Copper coin (US penny) (Mohs 3.5) · 🔪 Steel pocket knife (soft steel) (Mohs 5) · 🥃 Glass plate (Mohs 5.5) · 🔧 Steel file / hardened steel (Mohs 6.5)
Always test on an inconspicuous edge first. Save the test for unimportant specimens — better to use a streak plate or knowledge of locality + paragenesis.
Cite this entry
APA
MyMineralBox Editorial Team. (2026). Quartz. My Mineral Box. Retrieved May 23, 2026, from https://mymineralbox.com/mineral-encyclopedia/minerals/quartz/
MLA
MyMineralBox Editorial Team. "Quartz." My Mineral Box, 2026, https://mymineralbox.com/mineral-encyclopedia/minerals/quartz/. Accessed May 23, 2026.
Chicago
MyMineralBox Editorial Team. "Quartz." My Mineral Box. Last modified May 4, 2026. https://mymineralbox.com/mineral-encyclopedia/minerals/quartz/.
BibTeX
@misc{mmb_quartz,
author = {{MyMineralBox Editorial Team}},
title = {{Quartz}},
year = {2026},
publisher = {My Mineral Box},
url = {https://mymineralbox.com/mineral-encyclopedia/minerals/quartz/},
urldate = {2026-05-23}
}
