Cape May Diamonds are clear, water-worn quartz pebbles found on the beaches of Cape May, New Jersey. These specimens are often polished by wave action in the Delaware Bay, resulting in high clarity and naturally rounded shapes that mimic faceted diamonds.
Is this cape may diamond?
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 cape may diamond with a known reference. Cape May Diamond sits at Mohs 7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cape May Diamond leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cape May Diamond typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rounded pebbles.
Often confused with
Cape May Diamond vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside cape may diamond
Minerals reported to co-occur with cape may diamond. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 7
- Density
- 2.65 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Rounded Pebbles
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Lapidary, Jewelry
- Host rock
- Alluvial Deposits
- Typical price
- $1-20 per specimen
Where rockhounds find cape may diamond
Classic worldwide localities
- Cape May, New Jersey, USA
- Delaware Bay shores
Field-hunting tip
Look in alluvial deposits country — that is the host setting where cape may diamond typically forms. If you start seeing magnetite, ilmenite, garnet in float, you are in the right ground. Field specimens usually show a rounded pebbles habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cape may diamond on the map
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