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