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25 Gram Parcel, Larger Sized Clear To Champagne Sunstone

Catalog Number:  LGC 030510.3   Price:  $62.50 per 25 gram parcel

Champaign Sunstone Rough Parcel
Source: Plush, Oregon Mines and Fee Digging Claims

Size:  25 gram parcel, 4 to 6 pieces, 10 mm minimum cutting depth
Color:  Clear, Light Yellow, Champagne (Munsell 7.5Y:9/4 or GIA Y:2/2)
Refractive Index:  1.564 (alpha), 1.569 (beta), 1.576 (gamma) average
Optical Figure:  Biaxial, variable 54% Pos, 15% Neutral, 31% Negative
Specific Gravity:  2.725 average over range of 2.712 to 2.736




 

 

 

 


The Material:


Sunstone, a plagioclase feldspar.  The family of species in each parcel seems to range from Labradorite to Bytownite based on both R.I. and specific gravity tests conducted on a large population sampling (58 randomly selected tests).  Based on these tests the population seems to be approximately 75% Bytownite and 25% Labradorite, but this result is not certified and may be influenced by the amount of iron oxide or other material in solid solution.  Specific Gravity can also be effected slightly by the degree of slow crystalline unmixing of Albite and Anorthite components the material has experienced over geological times (Post-crystallization unmixing).  As a note of interest, unmixing during crystallization is the cause of the "Bluish" and "Silver" adularescence sheens (miscibility gap one), and "Multi-color" Labradorescence (miscibility gap two) sometimes seen in Plagioclase Feldspar.  Post-crystallization unmixing is also accompanied by internal crystalline dimensional changes that create stresses, and is one of the contributing reasons why large intact crystals are seldom found.  It also gives rise to the  "one time" thermoluminescence phenomenon seen when the feldspar is heated to a high temperature.

 

The Parcel:

 

These 25 gram parcels will contain between 4 and 6 pieces, more or less.  The parcels are filled by "luck of the scoop", and no attempt has been made to standardize the content other than by weight.  When the digital scale indication crossed over  25 grams the pour stopped.  The material has been acid cleaned to remove all surface oxides that confuse color evaluation, and conceal flaws.  Each piece has been eye examined over a lighted frosted glass inspection table, and if there are any pink, orange, red,  green, blue, or schiller pieces in the parcel it is only because of our oversight.   The basic colors present in the parcel range for nearly colorless to a light yellow "Champagne" color (Munsell  7.5Y: 9/4 or GIA  Y: 2/2).  Some pieces may have cracks or other flaws, but all have been judged to have at least 10 mm of clear cutting depth in the shortest of the LxWxD dimensions.  If not satisfied, please note our no questions asked return policy.  If you have any concerns or need a quantity adjustment please use the contact links provided.  All issues will be resolved.
 

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