• Chemistry: BaSi2O5 , Barium Silicate.
  • Class: Silicates
  • Subclass: Phyllosilicates
  • Uses: Only as mineral specimens.
  • Specimens

Sanbornite is a rare, but nicely named, phyllosilicate mineral. It is one of just a few barium minerals; other more common barium minerals being barite and witherite.

Barium tends to be a rather difficult element to place in minerals due to its large ionic size. Barium has an ionic radius of 1.34 Angstroms compared to the much more easily accommodated calcium's 0.99 Angstroms.

Barium's high density (its atomic number is 56) usually gives minerals that possess it a higher than average specific gravity. Sanbornite has a pearly luster and flashes of iridescence and can be a nice addition to someone's collection.


  • Color is usually a pale green, also gray, white or colorless.
  • Luster is pearly to vitreous or dull.
  • Transparency: Crystals are transparent to mostly translucent.
  • Crystal System is orthorhombic.
  • Crystal Habits include flat tabular or lamellar crystals.
  • Cleavage is good in one direction.
  • Fracture is uneven.
  • Hardness is 5
  • Specific Gravity is approximately 3.8 (above average for a non-metallic mineral)
  • Streak is white.
  • Other Characteristics: Displays iridescence between cleavage layers and lamellar twining is common.
  • Notable Occurrences are limited to Trumball Peak, Mariposa County and Big Creek, Fresno County, California, USA.
  • Best Field Indicators are crystal habit, color, cleavage, hardness and locality.
SANBORNITE specimens:
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SANBORNITE specimen snb-1
$ 24.00
Dims: 2.1 x 1.6 x 1.6" (2.3 x 4.1 x 4.1 cm)
Wt: 3.9 oz. (109.7 g)
El Rosario, Baja, California, Mexico
This small hand specimen consists of an apparently massive host rock that is made up of countless intergrown Sanbornite crystals. These crystals are so heavily intergrown that it is nearly impossible to detect any crystal form from them. The crystals have flat faces, though, and a flaky, micaceous consistency. They have a white color and a bright, subadamantine luster that also strongly resembles those of the mica group. As a matter of fact, the only visual difference between this material and muscovite is that muscovite usually has a lower luster! The matrix rock in which the Sanbornite is concentrated appears to be made of quartz or a feldspar, but there is actually more Sanbornite than matrix. Also trapped in the matrix are several incomplete formless, and deep red crystals of Gillespite, a barium iron silicate. Maybe our mineralogist, Dave, should buy this "namesake" piece!
no photo
snb-1 ($ 24.00)
El Rosario, Baja, California, Mexico
SANBORNITE specimen snb-2
$ 54.00
Dims: 4.0 x 2.7 x 0.5" (10.2 x 6.9 x 1.3 cm)
Wt: 5.68 oz. (161.0 g)
Esquire #1 Claim, Rush Creek, Fresno County, California, U.S.A.
This specimen consists entirely of crystalline Sanbornite. While the piece shows no definite crystal form, it has the flaky, micaceous crystalline tendencies of the species. Its largest surfaces are freshly-cleaved, whereas its thinner, side surfaces are coated with a thin, white crust or are rust-stained. Actually, it resembles mica in many respects, including its pale, greenish-white color and bright pearly luster. It does not flake as easily, however, and is more brittle than mica. It also lacks the transparence of muscovite and most other mica varieties at thin spots. Other than the aforementioned thin white crust, there is no host rock present.
no photo
snb-2 ($ 54.00)
Esquire #1 Claim, Rush Creek, Fresno County, California, U.S.A.
SANBORNITE specimen snb-3
$ 26.00
Dims: 2.8 x 1.4 x 0.5" (7.1 x 3.6 x 1.3 cm)
Wt: 1.75 oz. (49.7 g)
Esquire #1 Claim, Rush Creek, Fresno County, California, U.S.A.
This small hand specimen consists of a crystalline piece of Sanbornite. There is a consisderable amount of fresh breakage on the piece, but most of this is in the form of a large cleavage surface that constitutes one side of the flat specimen. It shows no definite visual crystal form, but has the classic crystalline tendencies of Sanbornite, including an almost micaceous cleavage. Its color is pale green, it has a pearly, almost micaceous luster, and is generally translucent, though some areas show impressive clarity. There is a thin crust of a dull, white material on a few of the edges that is moderately rust-stained, but no actual base rock is present.
no photo
snb-3 ($ 26.00)
Esquire #1 Claim, Rush Creek, Fresno County, California, U.S.A.
SANBORNITE specimen snb-4
$ 25.00
Dims: 5.3 x 2.6 x 0.9" (13.5 x 6.6 x 2.4 cm)
Wt: 7.5 oz. (215 g)
Big Creek, Fresno County, California. U.S.A.
This piece consists of a large, apparently split slab of crystalline Sanbornite. Though the material shows obvious evidence of cleavage, it has no apparent crystal shape. Its color is milky-white, its luster is bright and pearly, and it is effectively opaque at its present thickness. A small amount of massive quartz is embedded into one side of the slab.
no photo
snb-4 ($ 25.00)
Big Creek, Fresno County, California. U.S.A.
SANBORNITE specimen snb-5
$ 25.00
Dims:5.5x3.0x1.5" (14.0x7.6x3.8 cm)
Wt: 15.4oz. (437g)
Big Creek, Fresno cty., California
This is a large specimen of the mineral sanbornite on a bit of matrix material. Although this specimen is crystalline, nothing can be determined of the mineral's orthorhombic structure. This is not surprising, as sanbornite usually occurs as anhedral crystalline masses. This specimen does show the white color, pearly luster, and the nearly micaceous cleavage for the species.
no photo
snb-5 ($ 25.00)
Big Creek, Fresno cty., California


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