Mineral J

JADE, a gem variety of both Jadeite and Nephrite

 

VARIETY INFORMATION:

• VARIETY OF: both jadeite and nephrite
• USES: Gemstone and ornamental stone.
• COLOR: shades of emerald green as well as white, gray, yellow, orange and violet.
• INDEX OF REFRACTION: is approximately 1.66 (jadeite) and 1.62 (nephrite)
• HARDNESS: 6.5 - 7
• CLEAVAGE: does not apply due to massive nature of jade
• CRYSTAL SYSTEM: monoclinic
• SPECIMENS

Jade is a name that was applied to ornamental stones that were being brought to Europe from China and Central America. It wasn't until 1863 that it was realized that Jade was being applied to two different minerals. The two minerals are both exquisite for the purposes that jade is put to task and are hard to distinguish from each other. So what to do? Leave it alone and call them both Jade!

Jadeite is almost never found in individual crystals and is composed of microscopic interlocking crystals that produce a very tough material. Nephrite is actually not a mineral, but a variety of the mineral actinolite. The nephrite variety is composed of fibrous crystals inter-twinned in a tough compact mass. Other actinolite varieties are quite different from nephrite.

The toughness of jade is remarkable. It has a strength greater than steel and was put to work by many early civilizations for axes, knives and weapons. It was later that jade became a symbolic stone used in ornaments and other religious artifacts during the eons.

Today jade is still valued for its beauty. Its many colors are appreciated, but its the emerald green color that jadeite produces so well, that is highly sought after by artwork collectors. This emerald green jade called "Imperial Jade" is colored by chromium. Other colors are influenced by iron (green and brown) and manganese is thought to produce the violet colors. Nephrite is usually only green and creamy white, while jadeite can have the full range of jade's colors.

 

 

 

 THE MINERAL JADEITE

 

• Physical Properties: Click here
• Chemistry: Na(Al, Fe)Si2O6, Sodium Aluminum Iron Silicate.
• Class: Silicates
• Subclass: Inosilicates
• Group: Pyroxene
• Uses: as an ornamental stone used for carvings and semi-precious to precious stone used in jewelry
• Specimens

Jadeite is one of the two minerals called jade. The other jade mineral is nephrite, which is a variety of actinolite. Jade has been used for eons in China and Central America as an ornamental and religious stone of deep significance. The nephrite jade was used mostly in China, although both have been used in both regions. Nephrite is more abundant than jadeite and has few color varieties, ranging only from creamy white to green.

Jadeite is found in strongly metamorphosed sodium-rich serpentinous rocks, and is named from the Spanish "piedra de ijada" (stone of the side) as it was thought to cure kidney stones and other kidney ailments.

Jadeite has many color varieties, and while green jadeite is most recognizable as jade, it is more commonly found as a grayish green, and may also be white, a pale blue-gray, or even a pale purple.

 

PHYSICAL CHARACTERISTICS:

• Color is usually green to grayish-green, white, pale shades of blue or purple, may also be yellow or pink.
• Luster is vitreous.
• Transparency: examples are translucent.
• Crystal System is monoclinic; 2/m
• Crystal Habits Generally fine-grained fibrous, also massive or granular.
• Cleavage: is good but rarely observed.
• Fracture is splintery to uneven.
• Hardness is 6.5.
• Specific Gravity is approximately 3.25 - 3.35 (above average for translucent minerals).
• Streak is white.
• Associated Minerals are quartz, serpentine, nepheline, calcite, aragonite and vesuvianite.
• Other Characteristics: Fine grained jadeite is extremely tough and is actually stronger than steel.
• Notable Occurrences include San Benito County, California, Mexico, Japan, Tibet, and the best gem-quality from Myanmar (Burma).
• Best Field Indicators are toughness, fibrosity, typical green color and hardness.

 

   

THE MINERAL JAMESONITE

 

• Chemistry: Pb4FeSb6S14, Lead Iron Antimony Sulfide
• Class: Sulfides and Sulfosalts
• Uses: Mineral specimens
• Specimens

Jamesonite is one of a few sulfide minerals that form fine acicular crystals that appear as hair-like fibers. The fibers may be so thick as to cover a specimen with hair-like fibers or it may be sparsely dessiminated between other minerals and may be confused with actual hairs. Boulangerite and millerite are two other sulfides that form similar acicular crystals and can be mistaken for jamesonite. However, millerite is yellow and boulangerite has flexible crystals. Jamesonite also forms larger prismatic crystals that can be confused with stibnite. Jamesonite crystals have less definition in its crystals and are more brittle. Jamesonite is a sulfosalt, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs. Jamesonite has been called feather ore and grey antimony.

 

PHYSICAL CHARACTERISTICS:

• Color is dark gray.
• Luster is metallic and silky.
• Transparency Crystals are opaque.
• Crystal System: Monoclinic; 2/m
• Crystal Habits include dense or sparse felted masses of acicular crystals. Also in fiberous masses.
• Cleavage is good in one direction perpedicular to its length.
• Fracture is uneven.
• Hardness is 2 - 3
• Specific Gravity is 5.5-6.0
• Streak is gray-black.
• Associated Minerals include pyrite. sphalerite, galena, stibnite and arsenopyrite.
• Other Characteristics: Crystals are not flexible and are brittle.
• Notable Occurrences include Cornwall, England; South Dakota and Arkansas, USA; Zacatecas, Mexico and Rumania.
• Best Field Indicators crystal habit, brittleness, associations, color and luster.

 

 

 

    

THE MINERAL JAROSITE

 

• Chemistry: KFe3(SO4)2(OH)6, Potassium Iron Sulfate Hydroxide.
• Class: Sulfates
• Group: Alunite
• Uses: Only as mineral specimens.
• Specimens

Jarosite is not a common mineral. It is closely related to the mineral natrojarosite. Jarosite is isostructural with natrojarosite which means that they have the same crystal structure but different chemistries. In this case, jarosite contains potassium instead of natrojarosite's sodium (natro is derived from the Latin for sodium, natrium, from where sodium gets its symbol, Na). The two minerals are difficult to distinguish without a chemical test.

Both minerals are isostructural with alunite with a formula of KAl3(SO4)2(OH)6, who lends its name to the Alunite Group of which all three minerals belong.

The symmetry of jarosite is the same as the members of the Tourmaline Group. Crystals of jarosite however do not form prismatic crystals like those of the typical tourmaline mineral. Jarosite's crystals are more flattened and resemble nearly cubic rhombohedrons. The "rhombohedrons" are actually a combination of two trigonal pyramids.

PHYSICAL CHARACTERISTICS:

• Color is an amber yellow or brown.
• Luster is vitreous to resinous.
• Transparency: Crystals are transparent to translucent.
• Crystal System is trigonal; 3 m
• Crystal Habits include tabular to flattened rhombohedral looking crystals. The "rhombohedrons" are actually a combination of two trigonal pyramids. Crystals are somewhat scarce and small, more commonly as earthy masses, films or crusts, botryoidal and granular.
• Cleavage is good in one direction but only seen in the larger crystals.
• Fracture is uneven.
• Hardness is 2.5 - 3.5.
• Specific Gravity is approximately 2.9 - 3.3 (average to slightly heavy for translucent minerals, but hard to obtain from crusts)
• Streak is a pale yellow.
• Associated Minerals are barite, turquoise, galena, goethite, limonite, hematite and other iron minerals.
• Notable Occurrences include Jaroso ravine, Sierra Almagrera, Spain and Iron Arrow Mine, Colorado; Maricopa Co., Arizona; Idaho and California, USA.
• Best Field Indicators are crystal habit, associations, color and hardness.

 

 

 

 

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)₂Si ₈(O, OH) - 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.

 

 

THE MINERAL JORDANITE

 

• Chemistry: Pb₁₄(As, Sb)₆S₂₃, Lead Arsenic Antimony Sulfide
• Class: Sulfides
• Subclass: Sulfosalts
• Uses: As a very minor ore of lead and arsenic and as mineral specimens.
• Specimens

Jordanite forms sharp, nicely formed crystals sometimes with deep striations. The contrasting dark gray to black, high lustered mineral sitting on a backdrop of massive white dolomitic marble makes for a very nice mineral display specimen. Jordanite is a rare sulfide mineral found mostly at the famous quarry of Lengenbach, Binnental, Valais, Switzerland. Most of the more exotic minerals from this site are arsenic sulfosalts, like jordanite, and other sulfides. Some of the rare minerals from here include: novakite, seligmannite, rathite, sartorite, smythite, wallisite, lengenbachite, bernardite, baumhauerite, arsenolamprite, liveingite, dufrenoysite, marrite, imhofite and hatchite to name a few. Jordanite is a mineral formed from hydrothermal solutions that intermixed with the local country rock's chemistry to produce some exotic mineral species. Jordanite is isomorphous with the mineral geocronite, Pb₁₄(Sb, As)₆S₂₃ which means that they both have the same structure, just different chemistries. In this case jordanite is the arsenic rich mineral and geocronite is the antimony rich mineral.

 

PHYSICAL CHARACTERISTICS:

• Color is a lead gray to black.
• Luster is metallic.
• Transparency: Crystals are opaque.
• Crystal System: Monoclinic; 2/m.
• Crystal Habits include deeply striated prismatic and dipyramidal crystals and pseudohexagonal twins; also globular and granular forms.
• Cleavage is poor in one direction.
• Fracture: Conchoidal.
• Hardness is 3.
• Specific Gravity is 5.5 - 6.4 (heavier than average for metallic minerals)
• Streak is dark brown.
• Associated Minerals include lengenbachite, pyrite, bournonite, seligmannite, breithauptite, nisbite, costibite, arsenopyrite, gudmundite, meneghinite, sphalerite and dolomite.
• Notable Occurrences are limited to the type locality, the Lengenbach Quarry, Binnental, Valais, Switzerland as well as Zuni Mine, Silverton, San Juan County, Colorado and Sinking Valley, Pennsylvania, USA.
• Best Field Indicators are crystal habit, locality, striations, associations and density.