All guides
Evergreen pieces — the comparisons, field tests and decisions that separate one thing from another. Revised in place rather than dated, so each shows when it was last reviewed.
Gold vs Pyrite: Six Tests That Settle It in Two MinutesSix field tests that separate real gold from pyrite, chalcopyrite and mica — using a knife, a ceramic tile and your hands. No chemicals required.
Calcite vs Quartz: How to Tell Them Apart Every TimeCalcite and quartz look almost identical and behave completely differently. Four tests — hardness, acid, cleavage and crystal shape — separate them in under a minute.
Hematite vs Magnetite: The Magnet and the Streak PlateTwo black iron minerals, two tests. A magnet and a ceramic tile separate hematite from magnetite reliably — here is why, and what to do about the confusing cases.
Jade or Serpentine? What Most Green Stone Actually IsMost green stone sold as jade is serpentine. Four practical tests — the knife test, heft, sound and translucency — tell you which one you have.
How to Tell If a Snake Is Venomous — And Why the Usual Advice Is WrongTriangular heads and slit pupils are the standard advice and both are unreliable. Here is what actually distinguishes venomous US snakes, and why location beats appearance.
Copperhead or Water Snake? The Band Shape Settles ItCopperhead bands are wide at the sides and narrow over the spine. Water snake bands are the reverse. That one difference resolves most sightings — here is how to read it.
Cottonmouth or Water Snake? Watch How It SwimsCottonmouths float high on the surface and gape to show a white mouth. Water snakes swim submerged and flee. Four tests you can run from the bank, plus why it matters.
Coral Snake or Kingsnake? The Rhyme Works — With Two CaveatsRed touches yellow, kills a fellow — the rhyme is accurate in the United States and dangerously wrong elsewhere. Plus a second check that is easier to see: the snout.
Rattlesnake or Bullsnake? Look at the Tail, Not the NoiseBullsnakes hiss, flatten their heads and buzz their tails convincingly enough to be killed as rattlesnakes constantly. One glance at the tail settles it.
Brown Recluse or Wolf Spider? Size Settles ItWolf spiders are big, hairy and patterned. Recluses are small and plain. Five differences you can check from a photograph, starting with the one that resolves most cases.
Black Widow or Common House Spider? Look UnderneathWidows and house spiders build the same messy web in the same dark corner. The red hourglass underneath is the whole test — plus three backup checks including the egg sac.
Overwatering or Underwatering? The Leaves Won't Tell YouBoth make a plant droop and yellow, and the treatments are opposites. The soil, the leaf texture and the recovery time separate them in under a minute.
Which Tomato Leaf Spot Is It? Rings, Dots and GreaseFour diseases spot tomato leaves and they need different responses. Concentric rings, tiny black dots and a greasy texture separate them — one of them needs acting on today.
Largemouth, Smallmouth or Spotted? Three ChecksThe three black bass share water and often share a limit — but not always. Jaw length, stripe direction and a rough patch on the tongue separate all three in seconds.
Walleye or Sauger? Look at the Tail and the Dorsal FinTwo features separate them, both on the fins, and both visible in a second. They frequently carry different limits and they hybridise, which complicates things further.