THE MINERAL OLIGOCLASE


Oligoclase is not a well-known mineral but has been used as a semi-precious stone under the names of sunstone and moonstone. Sunstone has flashes of reddish color caused by inclusions of hematite. Moonstone shows a glowing shimmer similar to labradorescence, but lacking in color. The display is produced from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a separating and layering of these two phases. The resulting shimmer effect is caused by a ray of light entering a layer and being refracted back and forth by deeper layers before it exits the crystal. This refracted ray has a different character than when it went in and produces the moonlike glow. Moonstone is an alternate birthstone for the month of June.

Oligoclase is a member of the Plagioclase Feldspar Group. The plagioclase series comprises minerals that range in chemical composition from pure NaAlSi3 O8, Albite to pure CaAl2 Si2 O8 , anorthite. Oligoclase by definition must contain 90-70% sodium to 10-30% calcium in the sodium/calcium position of the crystal structure. The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements.

All plagioclase feldspars show a type of twinning that is named after albite. Albite Law twinning produces stacks of twin layers that are typically only fractions of millimeters to several millimeters thick. These twinned layers can be seen as striation like grooves on the surface of the crystal and unlike true striations these also appear on the cleavage surfaces. The Carlsbad Law twin produces what appears to be two intergrown crystals growing in opposite directions. Two different twin laws, the Manebach and Baveno laws, produce crystals with one prominant mirror plane and penetrant angles or notches into the crystal. Although twinned crystals are common, single crystals showing a perfect twin are rare and are often collected by twin fanciers.

PHYSICAL CHARACTERISTICS:

  • Color is usually off-white or gray or pale shades of green, yellow or brown.
  • Luster is vitreous to dull if weathered..
  • Transparency crystals are translucent to transparent.
  • Crystal System is triclinic; bar 1
  • Crystal Habits include blocky, or tabular crystals. Crystals have a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. Twinning is almost universal in all plagioclases. Crystals can be twinned according to the Albite, Carlsbad, Manebach and Baveno laws. Oligoclase can be found as a major rock forming component in granites and syenites.
  • Cleavage is perfect in one and good in another direction forming nearly right angled prisms.
  • Fracture is conchoidal.
  • Hardness is 6 - 6.5.
  • Specific Gravity is approximately 2.64 - 2.68 (average)
  • Streak is white.
  • Associated Minerals are quartz, muscovite and K-feldspars.
  • Other Characteristics: index of refraction is 1.533 - 1.552. Lamellar twinning may cause a grooved effect on cystal and cleavage surfaces that appear as striations.
  • Notable Occurrences include Sri Lanka; New York, USA; Russia; Sweden and Canada.
  • Best Field Indicators are occurrence, twinning striations, shimmer, density and index of refraction.

Moonstone Jewelry - Hover over an item for more information
Marquise Moonstone and .34 ct. t.w. Diamond Ring in Sterling Silver
A study in the soothing effects of tone-on-tone styling, this marquise moonstone and .34 ct. t.w. diamond ring demonstrates the might of white. Sterling silver ring.Only $195.00 at Ross-Simons
no photoMarquise Moonstone and .34 ct. t.w. Diamond Ring in Sterling Silver
$195.00
Ross-Simons
Moonstone, .90ct t.w. Iolite Ring, Diamond Accents in Silver
The luminous tones of this ring's moonstone are brought out by a frame of .90 ct. t.w. marquise iolites and diamond accents. Sterling silver ring.Only $85.00 at Ross-Simons
no photoMoonstone, .90ct t.w. Iolite Ring, Diamond Accents in Silver
$85.00
Ross-Simons
Sterling Silver Rainbow Moonstone Men's Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $152.99 at JeGem.com
no photoSterling Silver Rainbow Moonstone Men's Pendant
$152.99
JeGem.com
Cabochon Multi-Stone, .40ct t.w. White Topaz Cluster Earrings Over Sterling
Pretty pastels in a pleasing mix. These cluster earrings mix together cabochons of orange moonstone, rose quartz, gray agate and white agate between ribbons of .40 ct. t.w. white topaz. Clip/post, 18kt yellow gold over sterling silver earrings.Only $206.50 at Ross-Simons
no photoCabochon Multi-Stone, .40ct t.w. White Topaz Cluster Earrings Over Sterling
$206.50
Ross-Simons
Moonstone Slice Drop Earrings With Diamonds in 14kt Yellow Gold
So dreamy, the iridescent oval drops of these moonstone slice earrings with .10 ct. t.w. of diamonds reflect the stone s storied history as a mystical gem. Hinged post, 14kt yellow gold earrings.Only $375.00 at Ross-Simons
no photoMoonstone Slice Drop Earrings With Diamonds in 14kt Yellow Gold
$375.00
Ross-Simons
Moonstone and .15 ct. t.w. CZ Drop Earrings in 14kt Gold Over Sterling
Bring an element of mystique to your wardrobe with this pair of drop earrings. Round moonstone cabochons, aswirl with subtle colors, are held in beautifully textured frames. .15 ct. t.w. of round brilliant-cut CZs trim the leverbacks. 14kt yellow gold...Only $105.00 at Ross-Simons
no photoMoonstone and .15 ct. t.w. CZ Drop Earrings in 14kt Gold Over Sterling
$105.00
Ross-Simons
Sterling Silver Rainbow Moonstone Stud Heart Earrings
Handmade by Master Artisan. See more details at JeGem.com.Only $86.99 at JeGem.com
no photoSterling Silver Rainbow Moonstone Stud Heart Earrings
$86.99
JeGem.com
Cabochon Multi-Stone, .30ct t.w. White Topaz Cluster Ring Over Sterling
This pastel ring clusters cabochons of orange moonstone, rose quartz, gray agate and white agate with ribbons of .30 ct. t.w. white topaz. 18kt yellow gold over sterling silver ring.Only $175.00 at Ross-Simons
no photoCabochon Multi-Stone, .30ct t.w. White Topaz Cluster Ring Over Sterling
$175.00
Ross-Simons
Sterling Silver Rainbow Moonstone Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $113.24 at JeGem.com
no photoSterling Silver Rainbow Moonstone Pendant
$113.24
JeGem.com
Multi-Shaped Moonstone Linear Earrings in 14kt Yellow Gold
These linear earrings drop long and luminous cascades of multi-shaped and bezel-set moonstones. Features pear-shapes, rounds, ovals, and triangular-shapes. Post/clutch, 14kt yellow gold earrings.Only $295.00 at Ross-Simons
no photoMulti-Shaped Moonstone Linear Earrings in 14kt Yellow Gold
$295.00
Ross-Simons
Mixed Cabochon Gem Ring in 18kt Gold Over Sterling. Size 5
This mixed cabochon gem ring features an oval carnelian with round gray moonstone and rose quartz, all polished smooth and pretty. 18kt gold over sterling silver ring.Only $95.00 at Ross-Simons
no photoMixed Cabochon Gem Ring in 18kt Gold Over Sterling. Size 5
$95.00
Ross-Simons
Multicolored Moonstone Cluster Ring in Sterling Silver
So posh is pastels. This cluster ring is a bubbly bauble of white, gray and peach moonstone cabochons. Sterling silver ring.Only $129.50 at Ross-Simons
no photoMulticolored Moonstone Cluster Ring in Sterling Silver
$129.50
Ross-Simons
Multicolored Moonstone Cluster Drop Earrings in 14kt Yellow Gold
Jumbles of faceted pear-shaped moonstones in gray, white, and peach make for a fun pair of cluster drop earrings. Leverback, 14kt yellow gold earrings.Only $125.00 at Ross-Simons
no photoMulticolored Moonstone Cluster Drop Earrings in 14kt Yellow Gold
$125.00
Ross-Simons
Moonstone, .33ct t.w. Diamond Ring in 14kt Yellow Gold Over Sterling
This ring's pear-shaped moonstone is faceted to draw out its pretty shades of blue and bordered by .33 ct. t.w. diamonds. 14kt yellow gold over sterling silver ring.Only $245.00 at Ross-Simons
no photoMoonstone, .33ct t.w. Diamond Ring in 14kt Yellow Gold Over Sterling
$245.00
Ross-Simons
Sterling Silver Rainbow Moonstone Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $163.49 at JeGem.com
no photoSterling Silver Rainbow Moonstone Pendant
$163.49
JeGem.com
Moonstone Jewelry - Hover over an item for more information
Peach Moonstone Shield Ring, White Topaz in 18kt Gold Over Sterling
The worldly charm of this peach moonstone shield ring calls to mind the opulence of Indian jewels. Center oval peach moonstone floats in a rippled frame of .70 ct. t.w. white topaz rounds with delightful results. 18kt yellow gold over sterling silver...Only $150.00 at Ross-Simons
no photoPeach Moonstone Shield Ring, White Topaz in 18kt Gold Over Sterling
$150.00
Ross-Simons
8.50ct t.w. White Topaz, Pear-Shaped Moonstone Drop Earrings in Silver
An RS exclusive. These gorgeous 8.50 ct. t.w. white topaz and pear-shaped moonstone drop earrings feature the moonstones swaying from icy-clear white topaz ovals. Post/clutch, sterling silver earrings.Only $120.00 at Ross-Simons
no photo8.50ct t.w. White Topaz, Pear-Shaped Moonstone Drop Earrings in Silver
$120.00
Ross-Simons
Marquise Moonstone and .34 ct. t.w. Diamond Ring in Sterling Silver
A study in the soothing effects of tone-on-tone styling, this marquise moonstone and .34 ct. t.w. diamond ring demonstrates the might of white. Sterling silver ring.Only $195.00 at Ross-Simons
no photoMarquise Moonstone and .34 ct. t.w. Diamond Ring in Sterling Silver
$195.00
Ross-Simons
Milky Aquamarine, Moonstone Mosaic Ring, Blue Topaz, Diamonds
Here's a fresh mosaic-style ring with moonstone, 2.20 ct. t.w. blue topaz, and milky aquamarine with halos of .20 ct. t.w. diamonds. Sterling silver ring.Only $250.00 at Ross-Simons
no photoMilky Aquamarine, Moonstone Mosaic Ring, Blue Topaz, Diamonds
$250.00
Ross-Simons
Gray Moonstone and 1.65 ct. t.w. Diamond Earrings in Sterling Silver
Flickering with faceted moonstones in a moody shade of gray, these elegant drop earrings are silhouetted by 1.65 ct. t.w. diamonds. Leverbacks, sterling silver earrings with a black rhodium finish.Only $750.00 at Ross-Simons
no photoGray Moonstone and 1.65 ct. t.w. Diamond Earrings in Sterling Silver
$750.00
Ross-Simons
Opaque Multi-Stone Mosaic Ring With Diamond Accents in 14kt Rose Gold
A warm collection of opaque and sparkling stones. This mosaic ring clusters rose quartz, orange agate, and peach moonstone with diamond accents sprinkled around. 14kt rose gold ring.Only $695.00 at Ross-Simons
no photoOpaque Multi-Stone Mosaic Ring With Diamond Accents in 14kt Rose Gold
$695.00
Ross-Simons
Multicolored Moonstone Cluster Drop Earrings in 14kt Yellow Gold
Jumbles of faceted pear-shaped moonstones in gray, white, and peach make for a fun pair of cluster drop earrings. Leverback, 14kt yellow gold earrings.Only $125.00 at Ross-Simons
no photoMulticolored Moonstone Cluster Drop Earrings in 14kt Yellow Gold
$125.00
Ross-Simons
Nashelle 14k-Gold Fill Heart Disc, Moonstone & Pink Quartz Initial Necklace
From humble beginnings to a fully staffed warehouse in Bend, Oregon, Nashelle remains true to its original purpose-handmade jewelry crafted with love and intention. Two dainty wire-wrapped gemstones add color and dazzle to a keepsake necklace with...Only $138.00 at Nordstrom
no photoNashelle 14k-Gold Fill Heart Disc, Moonstone & Pink Quartz Initial Necklace
$138.00
Nordstrom
Sterling Silver Rainbow Moonstone Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $217.49 at JeGem.com
no photoSterling Silver Rainbow Moonstone Pendant
$217.49
JeGem.com
Sterling Silver Rainbow Moonstone Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $115.49 at JeGem.com
no photoSterling Silver Rainbow Moonstone Pendant
$115.49
JeGem.com
Multi-Stone Bead Necklace in 14kt Gold Over Sterling
A feast for the eyes! This multi-stone bead and cultured baroque pearl necklace features amethyst, lapis, carnelian, chalcedony, turquoise, hematite, tiger s eye, agate, pink coral and moonstone and a gray baroque cultured freshwater pearl. Springring...Only $195.00 at Ross-Simons
no photoMulti-Stone Bead Necklace in 14kt Gold Over Sterling
$195.00
Ross-Simons
Moonstone and .22 ct. t.w. Diamond Ring in 14kt Gold Over Sterling
Polished to a smooth finish, the moonstone cabochon is haloed in .22 ct. t.w. diamonds. 14kt yellow gold over sterling silver ring.Only $192.50 at Ross-Simons
no photoMoonstone and .22 ct. t.w. Diamond Ring in 14kt Gold Over Sterling
$192.50
Ross-Simons
Graduated Moonstone Bead Necklace With 14kt Yellow Gold
A dreamy theme is yours with this graduated moonstone bead necklace. Rondelles range from 4x6mm to 7x13mm in size. Necklace features 14kt yellow gold spacers and fastens with 14kt yellow gold fishhook clasp.Only $185.00 at Ross-Simons
no photoGraduated Moonstone Bead Necklace With 14kt Yellow Gold
$185.00
Ross-Simons
Orange Moonstone, 2.00ct t.w. White Topaz Pendant Necklace Over Sterling. 18"
Soft and serene, this oval orange moonstone of 18 x 12mm catches the eye in an openwork border of 2.00 ct. t.w. white topaz rounds. Suspends from cable chain with lobster clasp. 18kt yellow gold over sterling silver necklace.Only $75.00 at Ross-Simons
no photoOrange Moonstone, 2.00ct t.w. White Topaz Pendant Necklace Over Sterling. 18"
$75.00
Ross-Simons
Sterling Silver Rainbow Moonstone Pendant
Handmade by Master Artisan. See more details at JeGem.com.Only $125.24 at JeGem.com
no photoSterling Silver Rainbow Moonstone Pendant
$125.24
JeGem.com
 


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