Crystal guide
How to Identify Amethyst
SiO₂ (Quartz)
Amethyst is purple quartz (SiO₂) colored by iron-related centers. It shares quartz’s Mohs 7 hardness and hexagonal crystal habit, and is one of the most photographed collector crystals — from single points to geode linings.
About Amethyst
Amethyst is purple quartz (SiO₂) colored by iron-related centers. It shares quartz’s Mohs 7 hardness and hexagonal crystal habit, and is one of the most photographed collector crystals — from single points to geode linings.
Amethyst is filed under crystals in the RockScan directory. Composition: Silicon dioxide with iron-related color centers. It forms via hydrothermal veins and geodes in volcanic rock. Typical occurrence: Brazil, Uruguay, Zambia, Russia. For the broader method, see how to identify rock types.
Amethyst properties
| Mohs hardness | 7 |
|---|---|
| Class | crystal |
| Scientific name | SiO₂ (Quartz) |
| Color | Pale lilac to deep royal purple |
| Luster | Vitreous |
| Crystal system / texture | Trigonal |
| Composition | Silicon dioxide with iron-related color centers |
| Formation | Hydrothermal veins and geodes in volcanic rock |
| Occurrence | Brazil, Uruguay, Zambia, Russia |
How to identify Amethyst
- Purple quartz; Mohs 7.
- Hexagonal prisms/points.
- Color often stronger at tips.
Lookalikes to rule out
- Fluorite (purple): Fluorite is Mohs 4 cubic; amethyst is Mohs 7 hexagonal quartz.
- Glass: Glass may have bubbles and molded seams; amethyst shows quartz crystal faces.
- Citrine (heat-treated confusion): Color differs; some heated amethyst becomes citrine-like — habit remains quartz.
Photo tips for Amethyst ID
- Show purple color zoning toward crystal tips.
- Cluster geode interiors need even light to avoid black crush.
- Include prism faces for quartz habit.
Snap one specimen in natural light, then open the result in the online studio or the rock identifier app.
Amethyst FAQ
How do you identify amethyst rock?
Purple quartz crystals with Mohs 7. Rule out softer purple fluorite by hardness and cubic cleavage.
Is amethyst a crystal or mineral?
Both language is used — it is the mineral quartz in crystal form. We place popular photo crystals under /crystals.
Amethyst vs purple glass?
Crystal faces, hardness, and lack of molded bubbles support amethyst.
How to identify amethyst rock
Searches for “how to identify amethyst rock” mix crystal points, geode interiors, and purple tumbled stones. Separate true amethyst from softer purple lookalikes with this checklist:
- Purple quartz: violet to deep purple color on a quartz body — often stronger toward crystal tips.
- Hardness 7: scratches glass; purple fluorite (~4) fails this test quickly.
- Habit: hexagonal prisms and pyramid terminations, or crystal linings inside geodes.
- Zoning: natural color zoning and crystal faces beat uniform dyed glass.
- Photo confirm: even light on clusters, then RockScan against fluorite and heat-treated citrine confusion.
Amethyst vs purple fluorite vs glass
- Purple fluorite: Mohs ~4 with cubic cleavage; amethyst is Mohs 7 hexagonal quartz.
- Glass: May show bubbles or mold seams; amethyst shows quartz crystal faces and hardness 7.
- Heat-treated / citrine confusion: Some commercial “citrine” is heated amethyst — color shifts toward yellow-orange; habit stays quartz.
Photo tips for amethyst clusters
Diffuse light to keep purple from crushing black; show color zoning toward tips and prism faces. Pair with geode, quartz, and fluorite guides, then confirm in the online studio or rock identifier app.
Related crystals to compare
Browse all: rocks · minerals · crystals · directory · what rock is this · rock vs mineral vs crystal. Confirm with the online studio or rock identifier app.