Provenite

About Smoky quartz

SiO₂

Smoky quartz is the grey-to-brown to black variety of quartz. Its colour comes from aluminium-based colour centres that are produced by natural irradiation, for example from radioactive elements in the surrounding rock. In polarized light it is dichroic, shifting from darker yellow-brown to lighter red-brown. Black or brown quartz that owes its colour to mineral inclusions or organic matter is often mislabelled as smoky quartz or morion.

Show 15 localities on the map

Photos of Smoky quartz

Cabinet-size smoky quartz crystals on green amazonite (specimen from Florissant area, Teller County, Colorado, USA).
Smoky quartz · Florissant area (Teller County)
Cabinet-size smoky quartz crystals on green amazonite (specimen from Florissant area, Teller County, Colorado, USA).
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Twisted smoky quartz crystal (gwindel) with a serrated edge (specimen from Graubünden, Switzerland).
Smoky quartz · Graubünden
Twisted smoky quartz crystal (gwindel) with a serrated edge (specimen from Graubünden, Switzerland).
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Solid smoky quartz specimen with sceptred, hoppered skeletal growth.
Smoky quartz · Goboboseb Mountains
Solid smoky quartz specimen with sceptred, hoppered skeletal growth.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Floater cluster of smoky quartz crystals ranging from prismatic to tabular, labelled Erongo Mountain.
Smoky quartz · Erongo Mountain
Floater cluster of smoky quartz crystals ranging from prismatic to tabular, labelled Erongo Mountain.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Deeply coloured smoky quartz gwindel (twisted crystal), labelled Göschenen Valley.
Smoky quartz · Göschenen Valley
Deeply coloured smoky quartz gwindel (twisted crystal), labelled Göschenen Valley.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Lustrous, gemmy dark smoky quartz crystal with accenting matrix, labelled Papachacra.
Smoky quartz · Papachacra
Lustrous, gemmy dark smoky quartz crystal with accenting matrix, labelled Papachacra.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Old smoky quartz crystal, labelled Conway, New Hampshire.
Smoky quartz · Conway (Redstone area), Carroll County
Old smoky quartz crystal, labelled Conway, New Hampshire.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source
Small gemmy smoky quartz crystal, labelled Little Three Mine.
Smoky quartz · Little Three Mine
Small gemmy smoky quartz crystal, labelled Little Three Mine.
Photo: Robert M. Lavinsky · CC BY-SA 3.0 · Source

Where Smoky quartz is found (15)

Argentina

Namibia

Switzerland

United Kingdom

United States

Identity

Variety of
Quartz
Also called
Morion (black smoky quartz); cairngorm (Scottish name for wine-yellow to brown smoky quartz)
Strunz
4.DA.05 · 4 Oxides and hydroxides
IMA status
Variety
Elements
Si, O

Physical properties

Color
Smoky grey, brown to black; the black end is called morion
Luster
Vitreous luster
Transparency
Variable
Mohs hardness
7
Density
2.65–2.66 g/cm³
Cleavage / fracture
Cleavage rarely observable and poor on {10-11}, {01-11} and {10-10}; rhombohedral parting; fracture conchoidal

Crystallography

Crystal system
Trigonal
Space group
P3₁21 or P3₂21
Typical habit
Prismatic crystals with rhombohedral terminations, as euhedral crystals grown into open cavities (granite, pegmatite, Alpine clefts); also rolled crystals in river gravels
Twinning
Very common: Dauphiné and Brazil penetration twins, Japan contact twins
Optical data
Uniaxial (+); omega = 1.544, epsilon = 1.553

Formation and use

Formation
Grows as free-standing crystals in open cavities: miarolitic cavities in granite and in pegmatite pockets, Alpine fissures (clefts) in granitic massifs, cavities in volcanic rocks, and veins in sandstone. The shade depends on how strongly the crystal was exposed to natural radiation from the surrounding granite.
Uses
Collector's specimens and gem or ornamental material; cairngorm gemstones from the Cairngorm Mountains supported a notable 19th-century local gem industry.
Stability and care
Most smoky quartz is naturally coloured, but some of the darker stones on the market are made by exposing clear quartz to gamma rays. Heating can destroy the colour centres, and the colour is reported to pale in sunlight only after a very long time. Do not heat, and avoid long exposure to strong light and heat.

Related minerals

Related minerals
Quartzrock crystalamethystcitrineprasioliterose quartz
Can be confused with
Black or brown quartz coloured by inclusions or organic matterbrown topaz (harder)brown diamond (much harder)black schorl tourmaline and melanite garnet (always opaque)

Sources

  1. SRC-084 · Book
    Handbook of Mineralogy - QuartzAnthony, J.W.; Bideaux, R.A.; Bladh, K.W.; Nichols, M.C. · 2001 · Mineralogical Society of America / Mineral Data Publishing
  2. SRC-085 · Database
    Quartz (Mindat.org mineral page)Mindat.org / Hudson Institute of Mineralogy
  3. SRC-122 · Database
    Smoky Quartz: Mineral information, data and localitiesMindat.org contributors · Mindat.org
  4. SRC-126 · Website
    Smoky quartz: The brown gemstone smoky quartz information and picturesMinerals.net · Minerals.net
  5. SRC-127 · Website
    Loch Avon (GCR 708) geositeScottish Geology Trust · Scottish Geology Trust GeoSites
  6. SRC-128 · Website
    Loch Avon GeoGuide page (Cairngorm Pluton granite)Scottish Geology Trust · Scottish Geology Trust GeoGuide
  7. SRC-133 · Museum / collection
    Info brochure: The Planggenstock treasure (EN)Natural History Museum Bern · Naturhistorisches Museum Bern
  8. SRC-136 · Database
    Hawk Feathers pocket, Smoky Hawk claim, Crystal Peak, Teller County, Colorado, USAMindat.org contributors · Mindat.org

Draft data from the Provenite workbook. Check entries against the cited sources before relying on them. Photos are open-licence images from Wikimedia Commons; the author and licence are given with each photo.