Name/Title
Elbaite ( Watermelon Tourmaline )Entry/Object ID
2004.1.17Description
Assemblage Zone: pegmatite dikes
Chemical Composition: (Na)(Al,Fe,Li,Mg)3 B3 Al3
Crystal System: Hexagonal System
Description: Common Name: Elbaite / Tourmaline
Chemistry: Na(Li,Al)3Al6Si6O18(BO3)3 (OH)4, Sodium Lithium Aluminum Boro-Silicate Hydroxide
Class: Silicates
Subclass: Cyclosilicates
Group: Tourmalines
Location: Found at Santa Rosa Mine, Itambacuri, Minas Gerais Southeast Region, Brazil
Description: Tall green (watermelon) with pink inside crystals
PHYSICAL CHARACTERISTICS:
Color is extremely variable with the most common colors being red, pink, green, blue, orange and yellow.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System: Trigonal; 3 m
Crystal Habit is typically elongated three, and occasionally six, sided prisms. The terminations can be either a simple to complex trigonal pyramid or 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 when three secondary prism faces are nearly as dominant as the three primary prism faces. Doubly terminated crystals are hemimorphic meaning that the two ends of the crystal are not exactly alike. The terminations on a doubly terminated crystal can have different slants to the pyramids on opposite ends. Acicular and massive forms can also be found.
Cleavage is absent although there is basal parting.
Fracture is uneven to conchoidal.
Hardness is 7 - 7.5
Specific Gravity is 3.0+ (average)
Streak is white.
Other Characteristics: Refractive indices = 1.62 and 1.68 .
Associated Minerals include those minerals associated with granitic pegmatites and metamorphic rocks such as micas, feldspars, quartz and even other gem minerals such as beryl, garnets, spodumene and topaz.
Best Field Indicators are crystal habit, triangular cross-section, color and hardness.
Type of Fossils Present: None
Fracture: Conchoidal
Grain Size: Crystalline
Hardness: 7 Quartz
Luster: Glassy
Occurrence: Forms in igneous and metamorphic rock. Tourmaline is found in the US and through the world wherever coarse granitic rocks and their related pegmatite dikes come to the surface.
The northeastern portion of the state of Minas Gerais, Brazil, contains the world's greatest concentration of complex granitic pegmatites, which are especially noted for the production of gem beryl, chrysoberyl, topaz, tourmaline, and kunzite. Pegmatite gemstones were first found in this region over 400 years ago; in the last 100 years, Brazil has supplied most of the world market for these five gemstones. As the first of a series of articles on this region and these gem materials, this article reviews the early exploration for gemstones, their occurrence, and the mining methods and miners responsible for the development of the deposits. Focus is then given to some of the major deposits of aquamarine and other beryls, especially in the Teófilo Otoni—Marambaia and Jequitinhonha River valley districts
Pressure: High
Rock Color: Light
Rock Origin: Terrestrial
Rock Type: Metamorphic
Specific Gravity: 3.0 - 3.3
Surface Process: Not apparent
Streak: white
Temperature: High
Texture: Crystalline
Variety: Elbaite belongs to the group of minerals known as the Tourmalines. It is the most colorful member of this group. Elbaite is often cut as a gemstone, sliced into colorful cross-sections or simply appreciated as natural specimens by millions of rock collectors. The many varied colors of Elbaite make it arguably the most colorful of the precious stones. Elbaite contains many variety names based on color. A beautiful blue variety is called indicolite (also known as indigolite), the pink to red variety is called rubellite, the green variety is known as verdelite, while the most famous variety is a pink and green combination called watermelon tourmaline. Often a specimen can have more than one color zone in the same crystal. These zones can alternate in color from the inside to the outside or from the top to bottom. Elbaite is strongly pleochroic which means that a transparent crystal will appear darker when viewed down the long axis of the crystal. A green or blue Elbaite can appear black when viewed from such an angle.Collection
Suomynona Mineral CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationDimensions
Width
8-5/16 inDepth
3-1/2 inLength
14 inWeight
21 ozDimension Notes
Dimension taken at widest pointsLocation
Category
PermanentMoved By
Curtis GardnerDate
May 25, 2023Notes
Added current locationLocation
Container
centerDrawer
north sideShelf
top tier, top tierWall
centerRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Wendy MondryDate
December 26, 2008Location
Container
centerDrawer
top tierShelf
north side, north sideWall
centerHallway
Discovery HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Wendy MondryDate
December 26, 2008Location
Cabinet
Case #56Wall
CenterBuilding
Freida Smith HallCategory
Permanent