Antigorite
Current inventory:  0 gems
 

  
Antigorite is named after its discovery locality of Valle di Antigorio, Domodossola, Piedmont, Italy.

Discovered in 1840;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Mg;Fe²⁺)₃Si₂O₅(OH)₄

Magnesium Iron Silicate Hydroxide

Molecular Weight:

300.77 gm

Composition:

Magnesium

18.18 %

Mg

30.15 %

MgO

Iron

13.93 %

Fe

17.92 %

FeO

Silicon

18.68 %

Si

39.95 %

SiO₂

Hydrogen

1.34 %

H

11.98 %

H₂O

Oxygen

47.88 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.27-10

Nickel-Strunz 10th Ed. ID:

9.ED.15

9 : SILICATES (Germanates)
E : Phyllosilicates
D : Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets

Related to:

Serpentine Group (also known as Kaolinite-Serpentine Group). Polymorphous with Clinochrysotile, Lizardite, Orthochrysotile, and Parachrysotile.

Members of Group:

Serpentine Group (also known as Kaolinite-Serpentine Group): Amesite, Antigorite, Berthierine, Brindleyite, Caryopilite, Chrysotile, Clinochrysotile, Cronstedite, Dickite, Fraipontite, Greenalite, Halloysite, Kaolinite, Kellyite, Lizardite, Manandonite, Nacrite, Népouite, Odinite, Orthochrysotile, Parachrysotile, Pecoraite

Varieties:

Al-Antigorite, Andes Jade, Bowenite, Jenkinsite, Picrolite

Synonyms:

Baltimorite, Bastard Asbestos, Genthite, Gymnite, Iron-Gymnite, Nickel-Gymnite, Porcellophite, Protoantigorite, Septeantigorite, Thermophyllite, Williamsite, Yu yen shi stone, Yu yen stone, Zermattite

Crystal Data

Crystallography:

Monoclinic - Domatic

Crystal Habit:

Minute crystals, typically platy along [001], rarely elongated along [010]; some plates have rectangular outline due to cleavage; commonly bladed or fibrous.

Twinning:

May exhibit two- or three-fold twins rotated 60° about an axis [001].

Physical Properties

Cleavage:

Perfect on {001}, observed on {100} and {010}

Fracture:

Conchoidal or Splintery

Tenacity:

Brittle

Moh's Hardness:

3.5 - 4.0

Density:

2.50 - 2.60 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Green, Blue-Green, White; Colorless to pale Green in thin section.

Transparency:

Translucent to Sub-Opaque

Luster:

Resinous, Greasy, Silky, Waxy, Earthy

Refractive Index:

1.555 - 1.573  Biaxial ( - )

Birefringence:

0.005 - 0.006

Dispersion:

Weak; r > v

Pleochroism:

None

Occurances

Geological Setting:

Commonly replaces ultramafic rocks, pervasively or in crosscutting veinlets. As a replacement of siliceous dolostone along contacts with diabase sills.

Common Associations:

Chromite, Chrysotile, Magnetite, Olivine

Common Impurities:

Ni, Al, Mn

Type Locality:

Antigorio Valley, Ossola Valley, Verbano-Cusio-Ossola Province, Piedmont, Italy; Geisspfad area, Binn Valley, Wallis (Valais), Switzerland

Year Discovered:

1840

View mineral photos:

Antigorite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Antigorite is a member of the Serpentine group of minerals that also includes Bowenite, Lizardite and Williamsite. Most Antigorite is opaque and fibrous but a few locations produce beautiful, translucent, pale green material suitable for cabochons or carvings and rarely even faceted gems. Examples of this gemmy, translucent material from the Pennsylvania-Maryland border area are often referred to as Williamsite.

Sources of Antigorite include the type locality; Antigorio Valley, Piedmont, Italy; New South Wales, Australia; Tirol Austria; Liaoning Province, China; Nagasaki and Fukuoka Prefectures, Japan; Glen Urquhart, Scotland; and in the USA at Texas, Pennsylvania; Baltimore, Maryland; and Brewster, New York. Most of these locations produce opaque, fibrous material not suitable for faceted gems or cabochons.
 

  
Antigorite gems for sale: