- Name also: English Sandwort, Norwegian Sandwort
- Family: Pink Family – Caryophyllaceae
- Growing form: Perennial herb. Runnerless, loosely tufted.
- Height: Under 5(–10) cm (2(–4) in.) Stem limp–ascending, glabrous, sparsely branched.
- Flower: Corolla regular (actinomorphic), white, approx. 1–1.5 cm (0.4–0.6 in.) wide; petals 5, entire, approx. 5 mm (0.2 in.) long, slightly longer than sepals. Sepals 5, tapered, with membranous margins, 1-veined, glabrous. Stamens 8–10, anthers white. Pistil of 3 fused carpels, styles 3. Flowers 1–2(–3), axillary, flower-stalks 5–7 mm (0.2–0.28 in.).
- Leaves: Opposite, almost stalkless. Blade elliptic, spoon-like, 3–6 mm long, quite fleshy, glabrous or at base sparsely hairy along edges, (unclearly) 1-veined.
- Fruit: Egg-shaped, 6-valved, 3–5 mm (0.12–0.2 in.) long capsule. Seeds black, granular.
- Habitat: Gravels in lower alpine tundra. Requires alkaline soil (is calciphile).
- Flowering time: July–August.
- Endangerment: Endangered, protected in the whole of Finland.
Many small members of the Pink family are difficult to identify. Arctic sandwort looks a lot like its close relatives, like the protected fringed sandwort (A. pseudofrigida), although its leaves are not fleshy and its petals are clearly longer than its sepals. Both species are very rare: Arctic sandwort grows sparsely only on the tundra of Saana and Malla in Enontekiö at a height of 800 metres, while fringed sandwort grows deep in the forest belt in crevices in the rugged canyons of Kuusamo and Salla. Most Finnish stands of fringed sandwort can be found on the banks of the rivers Kitka, Oulanka and Savina. There is a distance of about 500 km between these two species’ stands, so there is no danger of confusing them.
Apart from genus _ Arenaria_, other groups of small, white-flowered members of the Pink family in northern Finland are genus Minuartia sandworts (stichworts) and genus Sagina pearlworts. They have clearly smaller flowers and wider leaves than genus Arenaria.