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Hessonite (a variety of Grossular Garnet)

Discovery year unknown; IMA status: Not Valid (a variety of Grossular Garnet)

Chemistry

Chemical Formula:

Ca₃Al₂(SiO₄)₃ + Fe

Calcium Aluminum Iron Silicate

Molecular Weight:

450.45 gm

Composition:

Calcium

26.69 %

Ca

37.35 %

CaO

 (Grossular)

Aluminum

11.98 %

Al

22.64 %

Al₂O₃

Silicon

18.71 %

Si

40.02 %

SiO₂

Oxygen

42.62 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.08-70

Nickel-Strunz 10th Ed. ID:

9.AD.25

9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in [6] and/or greater coordination

Related to:

A variety of Grossular Garnet. Garnet Group. Grossular-Hibschite Series. Grossular-Katoite Series. Grossular-Uvarovite Series. Pyrope-Grossular Series.

Varieties:

None

Synonyms:

Cinnamite, Cinnamon Garnet, Cinnamon Stone, Essonite, False Hyacinth, Hyacinthoid

Crystal Data

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

Commonly in dodecahedra or trapezohedra, up to 15 cm, with striated faces. Also granular, compact, and massive.

Twinning:

None observed

Physical Properties

Cleavage:

None observed. Parting rarely observed on {110}.

Fracture:

Irregular/Uneven, Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.5 - 7.0

Density:

3.594 (g/cm³)

Luminescence:

Almost always non-fluorescent; may be a weak golden yellow under LW & SW UV.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Red, Orange, Brownish Red, Yellowish Brown  

Transparency:

Transparent to Opaque

Luster:

Vitreous, Sub-Vitreous, Resinous

Refractive Index:

1.731 - 1.754  Isotropic. RI increases with increasing iron contents (usually Fe3+).

Birefringence:

0.000 (Isotropic); may have weak strain birefringence of 0.0 - 0.005

Dispersion:

Strong

Pleochroism:

None

Occurances

Geological Setting:

In contact and regionally metamorphosed calcareous rocks, or rocks which have undergone calcium metasomatism; in some schists and serpentinites.

Common Associations:

Calcite, Dolomite, Epidote, Clinozoisite, Wollastonite, Scapolite, Vesuvianite, Diopside, Tremolite, Quartz.

Common Impurities:

Fe

Type Locality:

Unknown

Year Discovered:

Unknown

View mineral photos:

Hessonite Mineral Photos and Locations

More Information

Mindat.org (Hessonite)
Mindat.org (Grossular)
Webmineral.com (Grossular)

Hessonite is the more common variety of Grossular Garnet which is a member of the Garnet Group of minerals that includes Almandine, Andradite, Grossular, Pyrope, Spessartine and Uvarovite. Other varieties of Grossular Garnet are Hessonite, Rosolite and Tsavorite.

Hessonite Garnets range in color from cinnamon-brown to orange and have been called "Cinnamon Garnet" because of its color. The color is due to the addition of iron to its chemical formula. Gem quality Hessonite is found in Sri Lanka, Tanzania, Brazil and California, USA.

Hessonite is named from the Greek word "hesson" meaning "inferior", because of its inferior hardness compared to other varieties of Garnet.

Grossular, also known as Grossularite, is a calcium aluminum variety of the Garnet Group. The name Grossular is derived from the botanical name for the gooseberry, Ribes Grossularium, in reference to the green variety of Garnet that was originally found in the Vilyui River Basin, Eastern-Siberian Region, Russia. The name Garnet comes from the Latin word granatus meaning grain. This is from the comparison of garnet grains in rock looking like the dark red seeds of the Pomegranite fruit scattered on the ground. Tsavorite, Rosolite and Viluite are varieties of Grossular and are not recognized as distinct mineral species.

Hessonite gems for sale:

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