Name/Title
Benitoite / NeptuniteEntry/Object ID
2009.62.207Description
Description: Chemistry: BaTiSi3O9, Barium Titanium Silicate.
Class: Silicates
Subclass: Cyclosilicate
Location: Gem Mine California
Description: This a small specimen with a white matrix, some smooth milky white and some rough off white.
PHYSICAL CHARACTERISTICS:
Color is typically blue, but also colorless and yellowish.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System is hexagonal; bar 6 m 2
Crystal Habits include the flattened six faced dipyramid that has a distinct triangle shape often modified by minor faces. Also found as small grains.
Cleavage is absent.
Fracture is irregular.
Hardness is 6 - 6.5
Specific Gravity is approximately 3.6 (above average)
Streak is white.
Best Field Indicators are crystal habit, fluorescence, color, associations and locality.
Common Name: Neptunite
Chemistry: KNa2Li(Fe, Mn)2Ti2Si8O24, Potasium Sodium Lithium Iron Manganese Titanium Silicate
Class: Silicates
Subclass: Inosilicates
PHYSICAL CHARACTERISTICS:
Color is black to reddish black.
Luster is vitreous.
Transparency crystals are translucent to opaque.
Crystal System is monoclinic; 2/m
Crystal Habits include prismatic, elongated crystals with nearly square cross-sections. The terminations are modified and slanted dome faces. Also found massive and in disseminated grains.
Cleavage is perfect in two direction at 80 and 100 degree angles.
Fracture is splintery.
Hardness is 5.5
Specific Gravity is approximately 3.23 (slightly above average)
Streak is reddish-brown.
Best Field Indicators are crystal habit, internal reflection, streak, associations, color, and cleavage.
Occurrence: Notable Occurrences include only the mines of San Benito County, California, USA for good excellent crystals. SW Texas produces tiny grains in eocene sands as well as some other California localities.
Notable Occurrences include the famous San Benito Co., California site as well as Narsarssuk Greenland and the Kola penninsula, Russia.
Variety: Benitoite is a somewhat obscure, but wonderful gemstone mineral that was only discovered in the early 1900's. It has a sapphire blue color and was first thought to be a variety of sapphire. But x-ray studies showed that the crystal structure was unlike any mineral previously discovered. It is one of only a few minerals to crystallize in the bar 6 m 2 class called the ditrigonal-dipyramidal symmetry class.Collection
RAGM Mineral CollectionDimensions
Width
2-1/2 inDepth
1-1/4 inLength
4 inLocation
Location
Display Case
FS-9Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
ExhibitMoved By
Ian C.Date
January 29, 2025Notes
Location/ inventoryLocation
Display Case
FS-4Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 18, 2023
