Dravite

Object/Artifact

-

Crater Rock Museum

Name/Title

Dravite

Entry/Object ID

2014.1.77

Description

A(on display) & B(deaccessioned) Common Name: Dravite Chemistry: NaMg3(Al,Fe)6Si6O18(BO3)(OH)4 Group: Silicates Location: Australia Description: [B] A piece of Dravite (Toumaline) that is pyramidal at the top and has multiple flat surfaces on the edges. There are Mica deposits all around the piece which add a nice contrast to the otherwise mottled, dark brown Dravite. Physical Charateristics: Color is light brown to dark brown. • Crystal Habit is typically elongated three sided prisms. The terminations can be either a simple to complex trigonal pyramid or a flat basal face. The prism faces are striated lengthwise. In cross section, all tourmalines will appear predominantly triangular in shape with some crystals showing a hexagon. Doubly terminated crystals are hemimorphic meaning that the two ends of the crystal are not exactly alike. Massive forms can also be found. • Transparency: crystals are translucent to opaque. • Crystal System is Trigonal; 3m • Hardness is 7 - 7.5 • Specific Gravity is 3.2+ (slightly heavier than average) • Cleavage is absent although there is basal parting. • Fracture is uneven to conchoidal. • Luster is vitreous. • Associated Minerals include those associated with metamorphic rocks such as micas, feldspars and quartz. • Other Characteristics: crystals are brittle and refractive indices = 1.62 and 1.68 . • Notable Occurances include brazil and some other South American countries, and Africa. • Best Field Indicators are crystal habit, triangular cross-section, color and hardness.

Collection

RAGM Mineral Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Location

Location

Display Case

FS-9

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Permanent

Moved By

Ian Cunningham

Date

December 27, 2023