Aplite

A fine-to-medium-grained igneous rock of granitic composition, valued not for any single mineral it contains but for its unusually pure, glass-ready mix of potassium, aluminium, sodium and silica.

Historical usage

Britain's only significant aplite deposit is a dyke at Meldon, on the northern edge of Dartmoor, discovered either side of the Red-a-Ven Brook and first quarried from 1889. Its main use was as roadstone and railway ballast, but its unusual chemistry also drew a short-lived attempt at glass manufacture: a syndicate erected furnaces at the quarry around 1920, importing German and Dutch glassblowers to produce light-green medicine and cosmetic bottles from a mix of calcined aplite, marble, soda and manganese. Persistent difficulty producing clear glass forced the venture to lay off around 100 workers by February 1921, and it closed soon after; ordinary quarrying for aggregate and other uses continued at Meldon into the 1970s.

Value over time

Meldon's aplite needed almost no preparation to act as a glass-making base, costing as little as 15 shillings a ton against roughly £2 a ton for a conventional prepared glass-sand mixture -- on paper, a compelling cost advantage. In practice the venture could not turn that into a viable business: the glass it produced was persistently unclear, isolated Dartmoor offered no local pool of skilled glassworkers, and the factory folded within a year of production starting. Quarrying the rock itself for aggregate, however, remained commercially viable for decades after the glass venture failed.

Hazards & challenges

No hazard specific to aplite itself is well documented; as with any hard-rock quarrying, the generic risk is airborne silica dust and the resulting risk of silicosis for anyone cutting, crushing or calcining it without proper dust control.

Images

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Meldon Quarry — Devon (well documented example)
  Named 8 times in this record, first in the summary: “…out to sit beside one of the rarest rock exposures in Britain — an aplite dyke whose unusual chemistry produces minerals found nowhere else in…”

See every mine that worked aplite →

Sources

1. (secondary) Meldon Aplite Quarries, Devon (GCR block 36) — Geological Conservation Review / Scottish Geology Trust GeoGuide
2. (secondary) Meldon Glass Factory — Legendary Dartmoor
3. (secondary) Meldon, Devon — Wikipedia

Record created: 26 August 2026 · Last researched: 29 August 2026