Name/Title
Ulexite / ColemaniteEntry/Object ID
2009.62.24Description
Chemical Composition: see description
Crystal System: Triclinic System
Description: Common Name: Ulexite / Colemanite
Chemistry: NaCaB5O6(OH)6-5H2O, Hydrated Sodium Calcium Borate Hydroxide
Chemistry: CaB3O4(OH)3-H2O, Hydrated Calcium Borate Hydroxide
Group: Carbonates
Location: Borax- Boron, California, USA
Description: Has a cotton ball like crystal structure which is call acicular color is a creamy white with colemanite crystals coming out on the sides, both these minerals are borates so it is not suprising to find them together.
PHYSICAL CHARACTERISTICS OF ULEXITE:
Color is white or gray to colorless.
Luster is silky.
Transparency crystals are transparent to translucent.
Crystal System is triclinic; bar 1
Crystal Habits include tufts of acicular crystals called "cotton balls". Also as vein-like masses of parallel fibrous crystals.
Cleavage is perfect in one direction.
Fracture is fibrous.
Hardness is 2 (softer than a fingernail)
Specific Gravity is approximately 1.97 (very low density)
Streak is white.
Associated Minerals are borax, colemanite, hydroboracite and other borate minerals.
Other Characteristics: similar borate minerals have an alkaline taste, while ulexite is tasteless.
Best Field Indicators are crystal habit, associations, locality, density, unique optical property, and hardness.
PHYSICAL CHARACTERISTICS OF COLEMANITE:
Color is white to clear.
Luster is vitreous.
Transparency crystals are transparent to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits are quite variable, but include the short prismatic crystals always with complicated facets. Equant crystals that appear stubby and bead-like are also common. The crystals are sometimes flattened and can appear bladed. The terminations are either blunted or steeply pyramidal. Also massive, lamellar and granular habits are found.
Cleavage is perfect in one direction and distinct in another.
Fracture is uneven.
Hardness is 4.5
Specific Gravity is approximately 2.4 (somewhat lower than average)
Streak is white.
Associated Minerals are calcite, celestite, borax, ulexite, kernite, hydroboracite and other borate minerals.
Other Characteristics: exfoliates (peels off) upon heating.
Best Field Indicators are crystal habit, associations, locality, density, cleavage and hardness.
Fracture: Fibrous
Hardness: 2 Gypsum
Luster: Silky
Occurrence: Ulexite is found with the mineral borax and is directly deposited in arid regions from the evaporation of water in intermittent playa lakes. The precipitated ulexite commonly forms a "cotton ball" tuft of acicular crystals. Ulexite is also found in a vein-like bedding habit composed of closely-packed fibrous crystals, also known as "TV rock" or "TV stone" due to its unusual optical characteristics. The fibers of TV rock act as fiber optics, transmitting light along their lengths by internal reflection, and when a piece of TV rock is cut with flat polished faces perpendicular to the orientation of the fibers a good-quality specimen will display an image of whatever surface is adjacent to its other side.
Colemanite is a secondary mineral, meaning that it occurs after the original deposition of other minerals. The mineral borax is directly deposited in arid regions from the evaporation of water in intermittent lakes called playas. The playas form only in rainy seasons due to runoff from nearby mountain ranges. The runoff is rich in the element boron and is highly concentrated by evaporation in the arid climate. Eventually the concentration is so great that crystals of borax and other boron minerals form. Ground water flowing through the borax sediments at the bottom of the playa is believed to react with the borax and form other minerals such as colemanite. Colemanite is found in geodes within the borax sediment; its exact means of formation are still not well understood.
Rock Type: Sedimentary
Specific Gravity: 1.97 - 2.4
Streak: White
Texture: Microcrystaline
Variety: Ulexite is a structurally complex mineral, with a basic structure containing chains of sodium, water and hydroxide octahedra. The chains are linked together by calcium, water, hydroxide and oxygen polyhedra and massive boron units. The boron units have a formula of B5O6(OH)6 and a charge of -3, and are composed of three borate tetrahedra and two borate triangular groups.
Colemanite, like other borates, is a complex mineral, that is found in playa lakes and other evaporite deposits. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calciums, water molecules and extra hydroxides interspersed between the chainsCollection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
5 inDepth
6 inLength
7/8 inWeight
4.69 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
DS-6Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current locationLocation
Container
LeftDrawer
Top shelfShelf
Right side, Right sideWall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Scott LonganDate
August 5, 2009Location
Container
LeftDrawer
Top shelfShelf
LeftCabinet
Case #41Wall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
Permanent
