Tincalconite
Current inventory:  0 gems
 

  
Tincalconite is named from the Sanskrit word tincal for borax, plus the Greek word konis, meaning powder, in allusion to its composition and typical powdery nature.

Discovered in 1878; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Na₂(B₄O₇) • 5(H₂O)

Hydrated Sodium Borate

Molecular Weight:

855.86 gm

Composition:

Sodium

16.12 %

Na

21.73 %

Na₂O

Boron

15.16 %

B

48.81 %

B₂O₃

Hydrogen

3.30 %

H

29.47 %

H₂O

Oxygen

65.43 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

BORATES

Strunz 8th Ed. ID:

5/H.10-20

Nickel-Strunz 10th Ed. ID:

6.DA.15

6 : BORATES
D : Tetraborates
A : Neso-tetraborates

Related to:

Tincalconite-Borax Group.

Members of Group:

Tincalconite-Borax Group: Borax, Tincalconite

Varieties:

None

Synonyms:

Mohavite, Octahedral Borax, ICSD 66529, PDF 7-277

Crystal Data

Crystallography:

Trigonal - Trapezohedral

Crystal Habit:

Rare crystals are pseudo-octahedral, exhibiting {1011}, {0112}, and {0001}, to 1 cm; commonly as a powder. Cryptocrystalline - occurs as crystals too small to distinguish with the naked eye.

Twinning:

None

Physical Properties

Cleavage:

Indistinct on {001} 

Fracture:

Hackly

Tenacity:

Brittle

Moh's Hardness:

2.0

Density:

1.88 (g/cm³)

Luminescence:

White under both SW and LW

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless to white; colorless in transmitted light

Transparency:

Transparent to translucent

Luster:

Vitreous to dull

Refractive Index:

1.461 - 1.474  Uniaxial ( + )

Birefringence:

0.013

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

Metamorphosed bedded borate deposit in clay-shales. Typically a dehydration product of other borates.

Common Associations:

Borax, Kernite

Common Impurities:

n/a

Type Locality:

Searles Lake, San Bernardino County, California, USA

Year Discovered:

1878

View mineral photos:

Tincalconite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Tincalconite is a hydrous sodium borate mineral closely related to Borax, and is a secondary mineral that forms as a dehydration product of Borax. Borax often dehydrates to Tincalconite. Tincalconite typically occurs as a fine grained white powder. While most Tincalconite occurs through Borax being exposed to dry air, there are natural occurrences of Tincalconite, as in Searles Lake, California where it was first described in 1878. Tinalconite gems are very rare as most Tinalconite crystals are opaque and powdery and transparent to translucent crystals are rare.

In addition to several California and Nevada locations it is reported from Argentina, Italy, Turkey and Ukraine. Tincalconite is named from the Sanskrit word tincal for borax, plus the Greek word konis, meaning powder, in allusion to its composition and typical powdery nature.

Locations for Tincalconite: Probably more widespread than the few recorded localities suggest. In the USA, from the Kramer borate deposit, Boron, Kern County. and as crystals at Searles Lake, San Bernardino County, California. From the Tincalayu borax deposit, Salar del Hombre Muerto, Salta Province, Argentina. In the Kirka borate deposit, Eskiçehir Province, Turkey. At Larderello, Val di Cecina, Tuscany, Italy. From mud volcanoes, Kerch Peninsula, Ukraine.
 

  
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