Ulexite
Hydrated
Sodium Calcium Borate Hydroxide
NaCaB5O6(OH)6-5H2O
Ulexite
is a mineral which occurs in a silky white rounded crystalline masses
or in parallel fibers. The name, Ulexite has been given after a German
chemist G. L. Ulex of the 19th century, who discovered the mineral.
The structure of Ulexite is a bit complex. The basic structure
contain chains of sodium, water and hydroxide octahedrons. The chains
have been linked together by calcium, water, hydroxide and oxygen
polyhedra and massive boron units. The basic boron unit's formula is
B5O6(OH)6 and has a charge of -3. It is composed of three borate
tetrahedrons and two borate triangular groups.
Ulexite is found with the borax mineral and is directly deposited in
the arid regions from the evaporation of water in intermittent lakes
known as playas. Playas forms during the rainy seasons only due to the
runoff from the nearby mountains. These runoffs are rich in element
boron.
Ulexite is also found in the vein-like bedding habit composed of
closely-packed fibrous crystals. This varity of ulexite is called TV
Rock. It is very popular in many of the rock shops, particularly with
children. The fibers of the TV Rock is like fiber optics. It transmits
light along its lengths by internal reflection. A well polished flat
cut TV Rock displays an image of whatever surface is adjacent to its
other side.
Ulexite decomposes in hot water.
Physical Properties of Ulexite
| Color |
White of gray to
colorless |
| Luster |
Silky |
| Transparency |
Crystals are transparent to
translucent |
| Crystal system |
Triclinic; bar 1 |
| Crystal habits |
Tufts of acicular crystal known
as "cotton balls." It is also as vein-like masses of
parallel fibrous crystals. |
| Cleavage |
Perfect in one direction |
| Fracture |
Fibrous |
| Hardness |
2 (more soft than a fingernail)
|
| Specific gravity |
Approximately 1.97 (very low
density) |
| Streak |
White |
Associated Minerals of Ulexite
- Borax
- Colemanite
- Hydroboracite
- Other
borate minerals
Uses of Ulexite
- As
an ore of boron
- As
mineral specimens
Occurrences of Ulexite
-
California and Nevada in the USA
- Tarapaca,
Chile
- Kazakhstan
|
