Benitoite

Object/Artifact

-

Crater Rock Museum

Name/Title

Benitoite

Entry/Object ID

2014.1.114

Description

Chemical Composition: BaTiSi3O9 Crystal System: Hexagonal System Description: Chemistry: BaTiSi3O9, Barium Titanium Silicate. Class: Silicates Subclass: Cyclosilicate Location: Dallas Mine, San Benito Co., California Description: This triangular shaped piece has been cut on one edge and one larger surface The other larger surface has been acid etched to show the sapphire blue crystals. 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. Fracture: Irregular Hardness: 6 Orthoclase Luster: Vitreous 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. Rock Type: Sedimentary Specific Gravity: 3.6 Streak: White 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 Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Dimensions

Width

6-1/4 in

Depth

1-3/4 in

Length

7-3/4 in

Location

Location

Cabinet

H-1 front

Wall

North

Building

Storage (old gift shop upstairs)

Category

Permanent