How to Identify Amethyst
Amethyst is simply the purple variety of quartz — its color comes from trace iron and natural irradiation. That means it carries all of quartz's identifying traits: hardness 7, hexagonal crystals, and glassy conchoidal fracture.
Quick Facts
- hardness
- 7 (scratches glass)
- streak
- White
- luster
- Vitreous (glassy)
- color
- Pale lilac to deep violet-purple, often zoned
- crystal System
- Trigonal (hexagonal prisms with pyramidal points)
- cleavage
- None — conchoidal fracture
- specific Gravity
- 2.65
Where to Find It
Amethyst grows in cavities and geodes in volcanic rock, and in hydrothermal veins. The great sources are the basalt lava flows of Brazil and Uruguay, where huge amethyst geodes form, along with occurrences in Zambia, Mexico, and the US. In the field, look for purple-lined vugs in volcanic rock and loose crystal points weathered from veins.
What Amethyst Looks Like
- Purple color, from pale lilac to deep violet — often unevenly distributed.
- Color zoning: darker purple concentrated near the crystal tips or in angular bands, fading to clear or white toward the base — a strong natural-amethyst clue.
- Six-sided (hexagonal) prisms ending in pyramidal points, the standard quartz crystal habit.
- A glassy, vitreous luster and transparent-to-translucent body.
- Frequent geode habit: crusts of purple points lining a rounded cavity, thickest and darkest at the crystal terminations.
- Conchoidal fracture with sharp edges and no flat cleavage planes.
Simple Tests to Confirm It’s Amethyst
You can do these at home with basic tools. They won’t damage a good specimen.
Scratch-glass hardness test
Amethyst is quartz, hardness 7, so a point will scratch glass cleanly and resist a steel knife. This immediately separates it from softer purple look-alikes like fluorite (hardness 4), which a knife scratches easily.
Hexagonal crystal check
Examine crystal form with a hand lens. Amethyst forms six-sided prisms with pyramidal terminations and no flat cleavage faces. Fluorite, by contrast, forms cubes or octahedra with perfect cleavage — a completely different geometry.
Color-zoning inspection
Look for uneven, banded, or tip-concentrated purple. Natural amethyst is famously zoned, with color pooling near the terminations. A stone that is perfectly, uniformly saturated purple throughout is more suspicious of dye or glass.
Density / heft cross-check
Quartz has a specific gravity of 2.65 — moderate, not heavy. Fluorite (3.2) feels noticeably denser, and glass and dyed materials vary. Comparing heft, alongside the hardness test, helps confirm you are holding quartz rather than a heavier or lighter impostor.
Not sure if your specimen is Amethyst?
Get an AI-powered first guess from a photo, then use the tests above to confirm.
Look-Alikes & How to Tell the Difference
Fluorite (purple)
Purple fluorite is a classic confusion, but it is much softer (hardness 4) so a knife scratches it, it forms cubes/octahedra with four perfect cleavage directions, and it is denser than quartz. Amethyst is hard (7), has no cleavage, and forms hexagonal points.
Dyed quartz / dyed agate
Colorless quartz or agate dyed purple. The color often looks too uniform or concentrates in fractures under magnification. Physical tests match quartz (it is quartz), so rely on the unnatural, even color and pooling in cracks to spot dye.
Colored glass
Purple glass mimics faceted amethyst but is softer (~5.5, so it will not scratch quartz), may contain air bubbles or mold seams, and lacks natural color zoning and hexagonal crystal form.
Ametrine and heated amethyst
Ametrine is a natural amethyst-citrine mix (purple and yellow zones in one crystal). Amethyst also turns yellow-orange 'citrine' when heated. Both are still quartz — the point is that purple-and-yellow zoning or an unusually orange 'citrine' hints at heat treatment, which affects value more than identity.
Frequently Asked Questions
How can I tell if amethyst is real?+
Confirm it is quartz first: it should scratch glass (hardness 7), resist a steel knife, form six-sided crystals with pointed ends, and show glassy conchoidal fracture. Then look for natural color zoning — real amethyst usually has uneven purple concentrated near the tips. Hard, hexagonal, and zoned points strongly toward genuine amethyst; soft or perfectly uniform purple points toward fluorite, dye, or glass.
How do I tell amethyst from purple fluorite?+
Hardness and crystal form settle it. Fluorite is soft (4) and a steel knife scratches it; amethyst is hard (7) and scratches glass instead. Fluorite forms cubes and octahedra with perfect cleavage; amethyst forms hexagonal prisms with pyramidal points and no cleavage. Fluorite also feels denser in the hand.
Is heat-treated amethyst the same as citrine?+
Much commercial 'citrine' is actually amethyst that has been heated until its purple turns yellow, orange, or reddish-brown. Both are quartz, so they are chemically the same mineral, but heated amethyst often has a slightly more orange or burnt tone and can show remnant color zoning. Whether a yellow quartz is natural citrine or heated amethyst mainly matters for collectors and value, not for the basic 'is it quartz' question.
Why is some amethyst pale and some deep purple?+
The purple color comes from trace iron in the quartz activated by natural radiation, and the amount varies. Color also concentrates unevenly during growth, which is why zoning is common and tips are often darker. Prolonged sunlight or heat can fade amethyst, so deep, even color is prized — but perfectly uniform, intense color can also signal dye, so check the physical tests.
Can a photo app identify amethyst?+
A photo app can recognize amethyst's purple color, crystal habit, and geode setting and give a solid first guess. But color-based ID can be fooled by dyed quartz, fluorite, and glass, and a camera cannot measure hardness. Use the app to narrow it down, then confirm with the scratch-glass test and a look at the crystal form and color zoning.
Related identification guides
This field guide is educational. Visual identification and simple at-home tests are helpful first steps, but they are not a certified geological, gemological, or meteorite analysis. Verify valuable, hazardous, or scientifically important finds with a qualified expert.