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Gyrolite
Current inventory:  0 gems
 

  
Gyrolite is named from the Greek Guros meaning "circle" in allusion to the typical round form of the crystalline groupings.

Discovered in 1851;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

NaCa₁₆(Si₂₃Al)O₆₀(OH)₈•14(H₂O)

Hydrated Sodium Calcium Aluminum Silicate Hydroxide

Molecular Weight:

3,586.19 gm

Composition:

Sodium

0.64 %

Na

0.86 %

Na₂O

Calcium

17.88 %

Ca

25.02 %

CaO

Aluminum

0.75 %

Al

1.42 %

Al₂O₃

Silicon

18.01 %

Si

38.54 %

SiO₂

Hydrogen

3.82 %

H

34.16 %

H₂O

Oxygen

58.89 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.34-40

Nickel-Strunz 10th Ed. ID:

9.EE.30

9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands

Related to:

Reyerite Group, Gyrolite Subgroup

Varieties:

n/a

Synonyms:

Centrallasite, Centrallassite, Glimmer Zeolite, Gurolite

Crystal Data

Crystallography:

Triclinic - Pseudohexagonal

Crystal Habit:

As spherical to radial masses, to 5 cm; massive, platy or plumose aggregates; as fibrous layers.

Twinning:

At a microscopical scale by rotation of 120± and 240± (001).

Physical Properties

Cleavage:

Perfect basal; poor prismatic

Fracture:

Irregular/Uneven

Tenacity:

Flakes flexible

Moh's Hardness:

2.5

Density:

2.45 - 2.51 (g/cm³)

Luminescence:

Fluorescent; Short UV=white, Long UV=white

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless to White, may be Grayish, Tan, Yellowish, Brownish, or pale Green from inclusions; Colorless in thin section

Transparency:

Transparent to Translucent to Opaque

Luster:

Vitreous to Pearly

Refractive Index:

1.535 - 1.550  Uniaxial ( - )

Birefringence:

0.0140

Dispersion:

Weak; r > v

Pleochroism:

None

Occurances

Geological Setting:

As replacements of wall rocks and in vugs, amygdules, and veinlets in basalts; in hydrothermally altered rhyolites and sediments; in some ore deposits.

Common Associations:

Apophyllite, Stilbite, Laumontite, Thomsonite, Okenite, Tobermorite, Xonotlite, Calcite

Common Impurities:

Fe, Mg

Type Locality:

The Storr, Portree, Trotternish, Isle of Skye, North West Highlands (Inverness-shire), Scotland, UK

Year Discovered:

1851

View mineral photos:

Gyrolite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Gyrolite is a fairly common mineral but rarely found as a faceted gem. It often forms as nodular aggregates that can appear glassy, dull or even fibrous. Gyrolite usually forms individual round nodules as opposed to botryoidal or crustal growths. Many Gyrolite nodules form inside of volcanic bubbles called vesicles that create surreal landscapes of various minerals.

Gyrolite is found at numerous localities worldwide. At Portree, Isle of Skye and 'S Airde Beinn, Isle of Mull, Scotland. From Ballhenry, Co. Antrim, Ireland. At Ortano, Elba, and at Monte Biaena, Pannone, Trentino-Alto Adige, Italy. At Ljósá, Eysturoy, and Gjónoyri, Streymoy, Faeroe Islands. From Qarusait and Tapaursak, Greenland. In India, from Nasik, Poona, on Bombay Island and around Bombay, Maharashtra. In Japan, at Sawayama Lake, Nagano Prefecture; Irakawa, Yamagata Prefecture; and Otemo, Niigata Prefecture. In the USA, from Fort Point, San Francisco County, and in the New Almaden mine, Santa Clara County, California; from Yellowstone National Park, Wyoming; in the Goose Creek quarry, Leesburg, Loudoun County, Virginia. From 40 km southwest of Cape Blomiden, between Margaretville and Port George, Nova Scotia, Canada. A few other localities are known.

  
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