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  • Sanidine

Sanidine

Feldspar

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV
Published: June 2014
Modified: January 2022
Sanidine Polished Sanidine Rough
Table of Contents
  • General Information
  • Sanidine Colors
  • Countries of Origin
  • Care

Sanidine is a potassium-rich feldspar which is related to amazonite (microcline) and orthoclase by its chemistry. The name comes from the Greek sanis meaning “little plate” and idos that translates to “to see”. Specimens are not common and cutting grade material is hard to find. Carlsbad twining is common in mineral specimens. Sanidine gems that display adularescence, a mystical internal glow, are called moonstone. Colorless to yellow and pale brown gems have been found in Germany, Mexico, and Madagascar. Most larger gemstones come from Itrongay (Itrongahy), Madagascar.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Sanidine
Species
Feldspar
Transparency
Transparent - Translucent
Dispersion
Strength: Weak Fire Value: 0.012
Refractive Index
1.518-1.531
Birefringence
0.003-0.007
Optic Character
Biaxial
Optic Sign
Negative
Polariscope Reaction
Doubly Refractive (DR)
Fluorescence
SWUV: Inert to weak red-orange
LWUV: Inert to weak red-orange
Pleochroism
Unobservable
Hardness
6-6.5
Streak
White
Specific Gravity
Typical:2.600
Luster
Vitreous
Fracture
Conchoidal, Uneven
Cleavage
Perfect, in two directions
Chemical Name
Potassium or Sodium Aluminum Silicate
Chemical Formula
(K, Na)(AlSi3O8)

Crystal System
Monoclinic
Chemistry Classification
Silicate

Sanidine Colors

  • Brown Sanidine
    Brown
  • Yellow Sanidine
    Yellow
  • Colorless Sanidine
    Colorless

Countries of Origin

Myanmar; Niger (the); Cameroon; Papua New Guinea; Angola; Paraguay; Portugal; Oman; Armenia; Greece; Austria; Mongolia; Mozambique; El Salvador; Morocco; Unknown; Brazil; Algeria; Cabo Verde; Chile; Lesotho; Argentina; Iran (Islamic Republic of); United States of America (the); Hungary; Republic of Kosovo; Japan; Ukraine; Taiwan (Province of China); Bolivia (Plurinational State of); India; New Zealand; Canada; Vanuatu; Turkey; Namibia; Finland; Honduras; Italy; South Africa; Antarctica; Peru; Ethiopia; Germany; Yemen; Tanzania, United Republic Of; Afghanistan; Eritrea; Viet Nam; Czechia; Guinea; Egypt; Chad; Madagascar; Thailand; Equatorial Guinea; Kiribati; Libya; Saudi Arabia; Sweden; Malawi; China; Russian Federation (the); Poland; Slovakia; Bulgaria; France; Jordan; Serbia; United States Minor Outlying Islands (the); Comoros (the); United Kingdom of Great Britain and Northern Ireland (the); Romania; Syrian Arab Republic; Sri Lanka; Uzbekistan; Kenya; Switzerland; Spain; Djibouti; Azerbaijan; Nicaragua; Congo (the Democratic Republic of the); Denmark; Mexico; Uganda; Australia; Estonia; Indonesia

Care

Sanidine is brittle so gentle handling is recommended. Avoid ultrasonic cleaners.

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