Monzonite is an intrusive igneous rock characterized by an approximately equal ratio of plagioclase and alkali feldspar. It lacks the significant quartz content of granite and the high mafic mineral content of diorite, giving it a balanced, medium-grey granular appearance. Collectors typically find it in plutonic bodies where it is studied for its chemical composition and igneous petrology.
Is this monzonite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch monzonite with a known reference. Monzonite sits at Mohs 6-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Monzonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Monzonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: gray, light gray, pinkish gray.
- 5Look at form & habitTypical habit: phaneritic.
Often confused with
Monzonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside monzonite
Minerals reported to co-occur with monzonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Mohs hardness
- 6-7
- Density
- 2.6-2.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal habit
- Phaneritic
- Cleavage
- None
- Rarity
- Common
- Uses
- Decorative, Construction, Architectural Stone
- Host rock
- Plutonic Intrusions
- Typical price
- low, typically sold as bulk landscaping or architectural stone
Where rockhounds find monzonite
1 mapped spotsClassic worldwide localities
- Monzoni Mountains, Italy
- Sierra Nevada, USA
- British Columbia, Canada
- Harz Mountains, Germany
Field-hunting tip
Look in plutonic intrusions country — that is the host setting where monzonite typically forms. If you start seeing plagioclase, orthoclase, hornblende in float, you are in the right ground. Field specimens usually show a phaneritic habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Idaho — start trip planning there.
Common questions
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Find monzonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
