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.
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 |
| 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 |
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 |
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.