Loch Avon (Beinn Mheadhoin and eastern crags)

Minerals found here

Smoky quartz at Loch Avon (Beinn Mheadhoin and eastern crags)

The classic source of cairngorm, found in granite cavities with blue topaz and beryl.

Formula

SiO₂

Morphology

Euhedral crystals grown into open granite cavities; also rolled stones in river gravel

Color / luster

Wine-yellow to brown (cairngorm) in the river gravels; dark smoky crystals in the cavities

Associated minerals

Topaz (including rare blue topaz)beryl (small crystals enclosed in cairngorm)alkali feldsparmuscovitebiotite

Trace elements

Aluminium-related colour centres produced by natural irradiation (general for the variety, not locality-specific)

History

Gemstones from the district supported an important 19th-century industry, although the exact positions of the workings were not recorded. An early survey named the crags east of Loch Avon as a source of cairngorm.

Sources: SRC-127 SRC-128

About Smoky quartz →

Geology of the locality

Setting

Miarolitic cavities and pegmatite veins in the Main Granite of the Cairngorm Pluton (Geological Conservation Review site, SSSI); crystals also occur as rolled stones in the River Avon gravels.

Type

Hydrothermal

Host rock

Cairngorm Granite (Main Granite of the Cairngorm Pluton)

Region

Scotland

Country

United Kingdom

Coordinates are the centre of Loch Avon (from a travel guide page based on Wikidata). The exact in-situ source of the crystals cannot be pinpointed; the minerals may partly derive from glacial drift. As an SSSI, unauthorised sample collecting is an offence.

Sources: SRC-127 SRC-128 SRC-129

Sources

1. SRC-127 · Website
   Loch Avon (GCR 708) geositeScottish Geology Trust · Scottish Geology Trust GeoSites
2. SRC-128 · Website
   Loch Avon GeoGuide page (Cairngorm Pluton granite)Scottish Geology Trust · Scottish Geology Trust GeoGuide
3. SRC-129 · Website
   Loch AvonThe Great Britain Guide · thegreatbritainguide.com