Archive for the Feldspar Group Category

Sunstone

Refractive Index : 1.590 – 1.527

Optical Characteristic : DR, B-, AGG

Specific Gravity : 2.77 – 2.57

Formula : (Na,Ca)(Si,AI)4O8

Crystal System : Triclinic

Variety/Species : Oligoclase/Plagioclase

Species/Group : Feldspar group

Birefringence : 0.007 to 0.010

Dispersion : N/A

Hardness : 6 to 6.5

Toughness : poor

Ultrasonic : Never

Steam : Never

UV Long : Inert

UV Short : Inert

Pleochroism : None

Strength : N/A

Pleochroism Colors : None

Heat [...]

Labradorite

Refractive Index : 1.568 – 1.599 (+0.005 – 0.005)

Optical Characteristic : DR B +

Specific Gravity : 2.70 (+0.05 – 0.05)

Formula : (Ca,Na)(Si,AI)4O8

Crystal System : Triclinic

Variety/Species : Plagioclase Feldspar

Species/Group : Feldspar Group

Birefringence : 0.007 to 0.010

Dispersion : N/A

Hardness : 6 to 6.5

Toughness : Poor

Ultrasonic : Never

Steam : Never

UV Long : Inert to Weak

UV Short : Inert [...]

Moonstone

Refractive Index : 1.526 – 1.518 (+0.010 – 0.010)

Optical Characteristic : DR, biaxial negative

Specific Gravity : 2.58 (+0.03 – 0.03)

Formula : KAISi3O8

Crystal System : Monoclinic

Variety/Species : Orthoclase feldspar

Species/Group : Feldspar group

Birefringence : 0.005 to 0.008

Dispersion : 0.012

Hardness : 6 to 6.5

Toughness : Poor

Ultrasonic : Never

Steam : Never

UV Long : Inert to weak

UV Short : Inert [...]

Andesine

Refractive Index : 1.5590 – 1.568 (+/- 0.05)

Optical Characteristic : DR, Biaxial positive

Specific Gravity : 2.70 (+/- 0.05)

Formula : (Na,Ca)(Si,AI)4O8

Crystal System : Triclinic

Variety/Species : Plagioclase Feldspar

Species/Group : Feldspar Group

Birefringence : 0.007 – 0.010

Dispersion : N/A

Hardness : 6 to 7

Toughness : Poor

Ultrasonic : Never

Steam : Never

UV Long : Inert to Weak

UV Short : Inert to Weak

Pleochroism [...]