Sand & geology
The geology of the world's beaches
Every beach is a record of its watershed. The minerals, the colour, the grain size — all of it is the weathered story of the rocks upstream and the biology offshore. Here's a grain-level tour.
Featured sand stories
Papakōlea Beach
US · green
Papakolea is one of only four green-sand beaches on Earth. The color comes from olivine crystals — a silicate of iron and magnesium — eroded out of the nearby Puu Mahana cinder cone. Olivine is denser than the surrounding basaltic ash, so it accumulates here instead of being washed out to sea.
Punalu'u Black Sand Beach
US
Punalu'u's jet-black sand is ground basalt, formed when molten lava entering the Pacific shattered into fine fragments through thermal shock. Unlike the quartz-rich beaches of the mainland, none of this sand comes from rivers — it is all freshly minted volcanic rock.
Reynisfjara
IS · black
Reynisfjara's pitch-black sand is fragmented basalt from the Katla volcanic system, deposited by the turbulent North Atlantic. The beach is backed by columnar basalt cliffs where rapid cooling of thick lava produced regular hexagonal joints.
Glass Beach
US
Decades of municipal dumping at Fort Bragg produced the world's most famous glass beach. Relentless Pacific surf has tumbled the broken bottles into rounded, frosted pebbles of green, brown, white, and rare blue. The glass is gradually being worn away and the beach is no longer self-replenishing.
Whitehaven Beach
AU · white
Whitehaven's sand is 98-99% pure silica — unusually fine quartz that reflects sunlight rather than absorbing it, keeping the sand cool in tropical heat. Geologists believe the deposit was transported by ancient currents from a source still not conclusively identified.
Hyams Beach
AU
Hyams Beach held a Guinness World Record for the whitest sand. The grains are high-purity quartz with minimal iron-oxide staining — a combination rarely found outside Australia's east coast, where the right bedrock, climate, and littoral transport converge.
Kaihalulu Beach
US
Kaihalulu's red sand comes from iron-rich cinders eroded from the crumbling cliff of Ka'uiki Head. The vivid brick-red color reflects oxidation of iron in the volcanic ash — essentially rust, frozen into the rock millennia ago and now returning to the sea.
Navagio
GR
Navagio's sand is pale limestone gravel and fine carbonate, the weathered remains of the Triassic limestone cliffs that enclose the cove. The sand is noticeably brighter than surrounding beaches because it contains almost no silicate minerals — only dissolved and re-precipitated calcium carbonate.
Playa de Gulpiyuri
ES
Gulpiyuri sits 100 metres inland, in a sinkhole fed by seawater through a karst tunnel. Its sand is pure shell carbonate, washed in with each tide through the limestone aquifer — a rare inland beach that breathes with the Cantabrian Sea.
Shell Beach
GY
Guyana's Shell Beach is named not for decorative shells but for the immense bank of cockle and clam fragments that makes up its substrate. There is effectively no mineral sand — just millennia of molluscan carbonate, replenished by the Amazon's nutrient plume and deposited by coastal drift.
Porto Ferro
IT
Porto Ferro's orange-red sand is a mix of iron-oxide-rich quartz grains weathered from the surrounding Sardinian sandstone, combined with biogenic shell fragments. The combination produces a distinct rust tone that deepens when the sand is wet.
Ir-Ramla t' Għajn Tuffieħa
MT
Malta's Ramla Bay has brick-red sand from weathered iron-rich sandstone of the Upper Coralline Limestone cap. It is the most-pigmented sand on the Maltese islands and exists only because the red-bed source rocks outcrop directly above this single bay.
Browse by sand colour
White sand — quartz or pure carbonate
86 beaches
Golden sand — quartz with iron staining
37 beaches
Black sand — volcanic basalt
21 beaches
Grey sand — mixed volcanic and granitic
4 beaches
How to read Q, F, L
Q (quartz) is the survivor: weathered out of granite, extraordinarily stable, accumulates in low-latitude beaches through long sediment transport. F (feldspar) points to fresh crustal material — granite, diorite — eroded close to its source. L (lithic) is rock fragments, often volcanic or metamorphic, and dominates beaches near active margins. The ratio is a signature of what's upstream, and it changes over geologic time as climate and uplift shift.
Predicted regional composition from the GloPrSM model (Sharman et al., 2022). Curated geology drawn from Wikipedia and peer-reviewed sources; citations on each beach page. Generated April 19, 2026.