THE MINERAL JOAQUINITE-(Ce)

  • Chemistry: NaBa2FeCe 2(Ti, Nb)2(SiO3) 8O2(OH, F) - H2O,
    Hydrated Sodium Barium Iron Cerium Titanium Niobium Silicate Oxide Hydroxide Fluoride
  • Class: Silicates
  • Subclass: Cyclosilicates
  • Group: Joaquinite
  • Uses: Only as a mineral specimen
  • Specimens
Joaquinite, which was discovered in 1909, is a pretty rare mineral. It is most renown for its association with other exotic minerals such as the sapphire blue benitoite, the red-black neptunite and the snow white natrolite. If it were not for these minerals which are found in San Benito County, California; joaquinite might not be so well known. It forms typically small, sparkling, brown to yellow, well formed crystals usually scattered on massive green serpentine.

Joaquinite is a product of some very unusual hydrothermal solutions. These solutions contained the elements titanium, niobium, lithium, barium, niobium, manganese, fluorine, cerium and several others. Anyone of them by themselves is not that unusual, but together in one solution and in such high concentrations is quite unusual. How they came to be combined like this is not yet well understood, but their product of unusual silicate minerals is much appreciated.

Joaquinite lends its name to a group of similar minerals. The Joaquinite Group members are unusual cyclosilicate minerals. They are some of only a few four membered ring silicates. These silicates have four silicate tetrahedrons linked into a ring forming a distorted square-like structural element. The general formula of this group is A6(Ti, Nb)2Si8(O, OH)6 - H2O; where A can be either sodium, barium, cerium, iron, manganese and/or strontium. Joaquinite and strontiojoaquinite are monoclinic, while the other members are orthorhombic.

These are the members of the Joaquinite Group:

  • Bario-Orthojoaquinite (Hydrated Barium Strontium Iron Titanium Silicate Oxide Hydroxide)
  • Byelorussite-(Ce) (Hydrated Sodium Barium Cesium Lanthanum Manganese Titanium Silicate Fluoride Hydroxide)
  • Joaquinite (Hydrated Sodium Barium Iron Titanium Niobium Cerium Silicate Oxide Hydroxide Fluoride)
  • Orthojoaquinite (Hydrated Barium Sodium Cesium Iron Titanium Silicate Oxide Hydroxide)
  • Strontiojoaquinite (Hydrated Strontium Barium Sodium Iron Titanium Silicate Oxide Hydroxide)
  • Strontio-orthojoaquinite (Hydrated Strontium Barium Sodium Iron Titanium Silicate Oxide Hydroxide)

PHYSICAL CHARACTERISTICS:

  • Color is brown, orange-brown, yellow or honey-yellow.
  • Luster is vitreous to silky.
  • Transparency: crystals are transparent to translucent.
  • Crystal System is monoclinic.
  • Crystal Habits include small equant stubby or striated bladed crystals often scattered on the host rock.
  • Cleavage is not seen.
  • Hardness is 5 - 5.5
  • Specific Gravity is approximately 3.8 - 4.0 (above average for transparent minerals)
  • Streak is white.
  • Associated Minerals include the sapphire blue benitoite, the red-black neptunite, the snow white natrolite and massive green serpentine as well as microcline, quartz and aegirine.
  • Notable Occurrences include the Joaquin Ridge (hence the name), Mt. Diablo Range, Contra Costa County and the head waters of the San Benito River, San Benito County, California, USA and a few rare specimens have been found at Mont Saint-Hilaire, Quebec, Canada.
  • Best Field Indicators are crystal habit, associations, color and locality.
JOAQUINITE specimens:
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JOAQUINITE specimen joa-1
$ 30.00
Dims: 2.6 x 1.9 x 1.2" (6.5 x 4.8 x 3.0 cm)
Wt: 3.0 oz. (86 g)
Gem Mine, San Benito County, California, U.S.A.
This specimen consists of several tiny Joaquinite crystals that rest on a serpentine/natrolite base. The crystals generally do not exceed 1 mm in length or diameter and are difficult to study even under 10x magnification. They do appear to be in good condition, however, and appear to also have good monoclinic prismatic form, with a diamond-shaped cross-section. They have a moderate brown color and a pearly luster, and are accompanied by several shards of much larger, broken neptunite crystals.
no photo
joa-1 ($ 30.00)
Gem Mine, San Benito County, California, U.S.A.
JOAQUINITE specimen joa-2
$ 98.00
Dims: 2.4 x 1.9 x 1.4" (6.2 x 4.7 x 3.7 cm)
Wt: 2.6 oz. (75 g)
Dallas Gem Mine, San Benito County, California, U.S.A
Several tiny Joaquinite crystals rest on the decayed serpentine base of this hand specimen. These crystals do not exceed 0.1 (3 mm) and are in excellent condition, showing no appreciable damage. Their monoclinic prismatic form is difficult to study without magnification, but appears to be quite good. All have a mahogany-brown coloration and a greasy-to-pearly luster. They are accompanied by a few broken neptunite crystals and a small patch of massive natrolite.
no photo
joa-2 ($ 98.00)
Dallas Gem Mine, San Benito County, California, U.S.A
JOAQUINITE specimen joa-3
$ 25.00
Dims: 2.83x2.71x1.53in (7.19x6.90x3.89cm)
Wt: 6.46oz (183g)
M T Jeannes Pit #1, San Benito County, California, USA
This is not technically joaquinite, but rather Strontiojoaquinite (Hydrated Strontium Barium Sodium Iron Titanium Silicate Oxide Hydroxide), a very close relative, also monoclinic. It is the pale brown crust exposed over much of the host rock, and intermixed with quite a number of other minerals. There is no indication of crystal form in the dull, opaque mineral, except in a few tiny patches (mostly on the back) where a loupe reveals tiny transparent pale brown crystals.
no photo
joa-3 ($ 25.00)
M T Jeannes Pit #1, San Benito County, California, USA
 

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