A grain-by-grain atlas of the planet
Over 400 sand samples, each photographed under a microscope. Tap any pin to explore.
The Collection
What is The Sand Hunter?
A single grain of sand is a fragment of a mountain, a reef, a volcano or a seashell — a tiny record of where it came from. The Sand Hunter is a growing library of the world's sand, collected grain by grain and photographed under a microscope.
How the collection works
Each sample is gathered from a real place — a beach, desert, riverbank, lakeshore or volcanic field — logged with its coordinates, weighed for its dry density, and placed under the microscope. From those photographs we build a circular "medallion" portrait of the sand and estimate its character: its setting, its grain shape, and its dominant minerals.
Everything here comes from genuine samples and genuine measurements. Where a property is inferred from the imagery, location and density rather than laboratory analysis, it is marked AI estimate — an honest best-guess, not a lab result.
Reading a sample
Where the sand formed — Beach, River, Desert, Lake, Volcanic field, Glacial, or something in between.
Its make-up: Quartz, Carbonate, Volcanic, Mineral, Feldspathic, Lithic, Gypsum, Oolitic — or Mixed when no single kind dominates.
How travelled the grains are. Angular grains are young and close to their source; well-rounded grains have been tumbled by wind or water for a long time.
How much a fixed scoop weighs — heavier sands are rich in dense minerals (magnetite, garnet); lighter ones are full of porous shell or pumice.
Get in touch
A question, a correction, or a jar of sand you would like to send? Do get in touch — a great deal of this collection arrived because somebody did exactly that.
Support the project
The Sand Hunter is a labour of love, powered by samples mailed in from around the world. If it brought you a moment of wonder, you can buy me a coffee ☕ — it helps keep the microscope humming.
Just The Facts
Every imaged sample in the collection — its readings, what the grains are made of, and the story of the place it came from.
Property Definitions
A plain-English guide to the categories used to describe each sand sample.
Setting
Where the sand comes from — the kind of environment it was collected in. Setting is independent of what the sand is made of: a beach can be carbonate, quartz or volcanic. But it shapes everything else, because the environment determines how a grain was transported and worn.
| Setting | What it means | How it's identified |
|---|---|---|
| Beach | Ocean or sea shoreline | A coastal location |
| River | Riverbed or riverbank | An inland watercourse; the sand mirrors the rock upstream |
| Desert | Sand from an arid region — wind-blown dunes, or water-laid washes, alluvial fans and dry channels | An arid inland location; grain shape varies (see note below) |
| Lake | Lakeshore | An inland lake |
| Volcanic field | Scooped from a volcanic deposit — ash, lava field or crater (not a shoreline) | At or near a volcano, inland |
| Glacial | Left behind by a glacier (outwash or moraine) | A high-latitude or alpine glacial source |
| Mountain / Highland | Eroded from upland bedrock — a mountain stream, talus slope or alluvial fan, far from the sea | An inland mountain or highland location; grains are often sharp and little-travelled |
| Manufactured / Industrial | Collected from a plant, yard or worked site rather than a natural deposit — the sand was made, processed or graded by people | An industrial source; note this describes where it was obtained, which may say nothing about where the raw material came from |
| Other / Unknown | Doesn't fit the above, or the location is too vague to tell | Used for donated samples with only an approximate location |
A note on "Desert." Not all desert sand is dune sand. Many samples are collected from alluvial fans, washes or dry channels, where flowing water — not wind — shaped the grains. So a desert sample can be smooth and frosted (a classic wind-blown dune) or comparatively sharp and angular (sand recently washed down a channel). The Grain Shape (Roundness) reading tells you which story a given sample carries — and we record it as a subtype: smoothly rounded desert grains are tagged wind-blown dune sand, while sharper, water-laid grains are tagged wash / alluvial sand.
Sand Type
Every sample is given one primary type based on what it is mostly made of. Distinctive single-mineral varieties (olivine, garnet, etc.) are noted as a subtype rather than their own top-level type.
| Type | What it is | How to recognize it |
|---|---|---|
| Quartz Sand | Weathered silica — the "classic" beach sand | Glassy, translucent, clear-to-white grains; the default tan beach |
| Carbonate Sand | Biogenic — ground-up shell, coral and marine skeletons | White-to-cream; you can often spot shell or spiral fragments |
| Oolitic Sand | Ooids — tiny polished mineral "pearls" | Very uniform, smooth, round beads; almost too perfect |
| Volcanic Sand | Basalt, olivine or pumice from volcanic activity | Dark grey/black/green, angular, glassy shards |
| Mineral Sand | Dominated by one heavy mineral | A strong single colour: green (olivine), red (garnet), black (magnetite) |
| Feldspathic Sand | Feldspar-rich continental sand | Opaque, blocky, pink or tan grains (not glassy like quartz) |
| Lithic Sand | Whole rock fragments, many minerals | Grey/brown, chunky, visibly "rocky" bits |
| Gypsum Sand | Soft white evaporite mineral | Pure bright white, soft, matte |
| Mixed Sand | No single dominant origin | A varied jumble of grain types |
| Manufactured Sand | Sand that was deliberately made — or deliberately treated — because someone wanted sand | Unnaturally uniform colour or a glassy, slaggy look; shapes and sizes that no river or beach would produce |
A note on "Manufactured Sand." Sand is defined by the size of its grains, not by what they are made of or how they came to be — so a man-made material broken down to sand size is, quite properly, sand. This category exists for those, and it is a small group today that we expect to grow. The line we draw is intent: was this sand deliberately made, because someone wanted sand? Abrasive grit for sandblasting, the grit spread over fresh asphalt, glass crushed on purpose to rebuild a coastal marsh — all of these were created to be sand, for a reason, and they belong here. So does sand that was deliberately treated to turn it into a product: the dyed sand sold for aquariums and craft work may have started as perfectly ordinary grains, but somebody coloured them on purpose in order to sell them as sand, and that is enough.
Two things sit close to the line and fall outside it. The first is man-made material that nature turned into sand by accident. The sea glass at Fort Bragg, California began as bottles tipped over a cliff into the Pacific and was then tumbled smooth by decades of surf — the material is man-made, but the sand is not; the ocean made that, exactly as it makes any other beach, and nobody involved wanted sand. It is classed as Mixed Sand. The second is natural sand that has merely been sorted, washed or sieved by an industrial process. Sorting alters nothing about a grain — those are still ordinary quartz or shell, nobody made them and nobody changed them — so they keep their natural type and are marked with a subtype such as graded industrial sand instead. Adding something to a grain is a change; passing it through a sieve is not. That same distinction is why the Setting of a sample can read Manufactured / Industrial while its Type stays entirely natural: setting records where a sample was picked up, type records what it is actually made of.
Grain Shape (Roundness)
How sharp or smooth a grain's corners and edges are. Roundness is essentially a maturity gauge — the longer a grain has travelled and been worked by water, wind or ice, the smoother it becomes (wind-blown desert grains are often the most rounded of all, while glacier-carried grains stay sharp). Sharp, angular grains are young and close to their source; smooth, rounded grains have a long history of transport. The scale runs from 1 (sharpest) to 6 (smoothest).
| Rank | Roundness | How to recognize it |
|---|---|---|
| 1 | Very Angular | Sharp, jagged, fresh-broken edges; no wear at all |
| 2 | Angular | Sharp corners and edges, little rounding (fresh volcanic, crushed rock) |
| 3 | Sub-angular | Corners starting to soften, but flat faces and edges still clear |
| 4 | Sub-rounded | Corners clearly worn down, edges smoothed, original shape still readable |
| 5 | Rounded | Smooth ovoid, edges gone, few flat faces (mature beach or river) |
| 6 | Well-rounded | Polished, near-egg or sphere, no trace of original edges |
Mineral Content
A sample's composition is its "ingredient list" — the minerals and materials the grains are actually made of. Because composition is open-ended and estimated from a photo, it is described in tiers rather than exact percentages (a precise number would imply a lab measurement we haven't made). Each sample also has one dominant mineral — its single biggest ingredient — which is what the collection can be sorted and filtered by.
| Tier | Meaning | Rough share |
|---|---|---|
| Dominant | What the sand is mostly made of | more than half |
| Common | A clear secondary ingredient | roughly a fifth to a half |
| Minor | Present but subordinate | a small fraction |
| Trace | Just a sprinkle | barely present |
So a sample might read: "Dominantly biogenic carbonate, with minor quartz and a trace of dark lithic grains."
The minerals and components we identify, and how they're recognized under the microscope:
| Mineral / component | How to recognize it |
|---|---|
| Quartz | Glassy, translucent, clear/white/grey |
| Carbonate (biogenic) | Opaque white-cream; shell, coral or skeletal shapes |
| Feldspar | Opaque, blocky, pink or tan — chalkier than quartz |
| Basalt / rock fragments | Dull dark grey-to-black, angular |
| Volcanic glass | Shiny black or brown glassy shards |
| Olivine | Distinctive olive-green, glassy |
| Garnet | Red, pink or purplish, glassy |
| Magnetite / iron oxides | Opaque black, sometimes metallic (the "black sand" heavies) |
| Mafic minerals (epidote, amphibole, pyroxene) | Olive-green to black, often glassy; from volcanic and metamorphic rock, common in heavy, colourful sands |
| Hematite-stained grains | Rusty red or orange coated (iron-rich desert sands) |
| Gypsum | Soft, matte, pure white |
| Lithic (mixed rock) | Brown/grey multi-mineral "rocky" chips |
| Mica | Thin reflective gold or silver flakes |
| Slag glass (iron silicate) | Man-made. Dense, glassy, near-black with a hard shine and sharp conchoidal fracture — the waste glass left after smelting metal from its ore |
Dry Density
The one directly measured value on every card: how much a fixed scoop of the dried sand weighs, in grams per cubic centimetre. Heavy sands are rich in dense minerals like magnetite and garnet; light ones are full of porous shell, pumice or loosely-packing mica flakes. Packing matters as much as mineralogy — a fine, well-sorted, angular sand can bridge and trap pore space, and so weigh less than its minerals alone would suggest.