Geological curios
Amber droplets
Tiny droplets and chips of fossil tree resin from the Raritan Formation occasionally wash into Big Brook and a few other NJ creeks. Many contain microscopic insects. Genuine NJ amber is rare enough that most people hunt a lifetime without finding a piece — bag it carefully.
How to spot it
- ▸Translucent honey-orange to deep red; warm to the touch
- ▸Floats in salt water (fresh water test is unreliable)
- ▸Lighter than gravel of similar size — feels almost weightless
- ▸Glows under UV (long-wave, 365 nm) with a strong blue-green fluorescence
- ▸Smells faintly of pine resin if rubbed briskly
Easy to confuse with
- ·Iron-stained quartz (heavier, scratches glass)
- ·Worn brown beach glass (more opaque, doesn't fluoresce)
- ·Copal (recent tree resin — same color, but doesn't survive the salt-water float test as well)
Geological context
NJ amber is Late Cretaceous (~92 Ma). Two hundred-plus insect species have been described from it, including the oldest known mosquito.
Reported at these sites
About the category
Mineral curios — pyrite, amber, agates, concretions — that ride along in the same gravel as the fossils.