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.

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.

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).

What each one looks like

Real grains from the collection, photographed under the microscope (the zoom varies from sample to sample, so compare shapes, not sizes). Tap a sample name to see the whole sample.

Most of the collection sits in the middle of the scale: about half the samples are Sub-angular and a third Sub-rounded. Only one sample (No. 0007) reaches Well-rounded, and none is Very Angular yet.

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.

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:

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.

How Soft Is This Sand? (Underfoot)

The Sand Hunter Softness Scale estimates how a sand would feel under bare feet, from Silky down to Ouch. It is an AI estimate read from each sample's microscope images, scored 0–100 and grouped into five bands. A ? after the band means the images made it a harder call than usual.

The score adds up four things seen under the microscope, each rated 1–5:

It's about shape, not hardness. It's often said that quartz beaches feel soft because quartz is "softer" — but quartz is one of the hardest common minerals, far harder than the shell and coral that make up many tropical beaches. The difference is shape. Quartz that has travelled a long way arrives small and rounded, and rounded grains roll. Shell and coral fragments are geologically young and still angular, so they lock together and crunch.

It rates the sample, not the whole beach. One beach holds several sands. At the waterline, waves wash the fines away and leave cleaner, sometimes coarser sand. Higher up, storm waves throw the coarsest material onto the berm. Behind that, wind can only lift the finest grains, so dune and wind-blown sand is usually the best sorted and most rounded — the likeliest to be Silky. Most samples in this collection were taken near the water. And wet sand at the waterline always feels firm, which a dried sample can't show.

A few samples are rounded pebbles rather than sand. They would score falsely soft, so they are marked Not rated (gravel).