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Heulandite
Current inventory:  0 gems
 

Chemistry:  (Ca,Na)_2-3Al₃(Al,Si)₂Si₁₃O₃₆•12H₂O
[Hydrated Sodium Calcium Aluminum Silicate]

Discovered in 1822;   IMA status: Valid (pre-IMA; Grandfathered).
Heulandite is named after John Henry Heuland (1778-1856), a British mineral collector and dealer.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/J.23-10

Nickel-Strunz 10th Ed. ID:

9.GE.05

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H₂O; zeolite family
E : Chains of T₁₀O₂₀ Tetrahedra

Related to:

Zeolite Group. Heulandite - Barium - Brewsterite Series. Clinoptilolite-Ca - Heulandite-Ca Series. The calcium analogue of Heulandite-Ba, Heulandite-K, Heulandite-Na and Heulandite-Sr.

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals commonly tabular and elongated, widest at the center, hence called "coffin-shaped," to 12 cm; also granular to massive.

Twinning:

With [100] as twin and contact plane.

Physical Properties

Cleavage:

[010] Perfect

Fracture:

Sub-Conchoidal to Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

3.5 - 4.0

Density:

2.10 - 2.20 (g/cm³)

Luminescence:

None

Radioactivity:

Barely Detectable; GRapi = 8.68 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Colorless, White, Gray, Green, Pink, Yellow, Red, Brown and Black

Transparency:

Transparent, but most often Translucent to Sub-Translucent

Luster:

Vitreous, Pearly on cleavages

Refractive Index:

1.491 - 1.512  Biaxial ( + )

Birefringence:

0.0030 - 0.0110

Dispersion:

Distinct, Crossed; r > v

Pleochroism:

None

Occurances

Geological Setting:

In cavities in basalts; in highly weathered andesites and diabases; as a devitrification product of volcanic glasses and tuffs.

Common Associations:

Apophyllite, Calcite, Datolite, Zeolites

Type Locality:

Linópolis, Divino das Laranjeiras, Doce valley, Minas Gerais, Southeast Region, Brazil

Year Discovered:

1822

View mineral photos:

Heulandite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Heulandite is one of the members of the Zeolite Group of minerals that includes many minerals and these gem-type minerals: Analcime, Chabazite, Heulandite, Mordenite, Natrolite, Pollucite, Scolecite, Stilbite, Thomsonite and Yugawaralite. Heulandite is one of the most common and one of the most well known members of the Zeolite Group. It forms complex and unique crystals with a nice pearly luster and beautiful shades of pinks, greens and yellows. Crystals are rarely transparent, but do have a nice translucency to them.

There are many locations for Heulandite but some of the best specimens come from Linópolis, Divino das Laranjeiras, Doce valley, Minas Gerais, Southeast Region, Brazil; Nasik and Pune (Poonah) Districts, Maharashtra, India; Drio le Pale, Buffaure Group, Fassa Valley, Trento Province, Trentino-Alto Adige, Italy; Rats Nest Claim, Challis, Custer County, Idaho, USA.
 

  
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