Materials
/
Montebrasite
Montebrasite
Refractive Index
1.6059–1.6240
Abbe Number
74.3–86.5
Crystal System
Isotropic (cubic)
Formation
Natural
Dispersion Data
Measured (published fit)
Fits
2
Refraction Fits
Fit #1
Shannon / Cauchy
n
n
=
1.6240
V
D
=
74.3
n
400
450
500
550
600
650
700
750
1.610
1.620
1.630
1.640
1.650
n
2
=
1
+
0.626
(
λ
2
−
0.008466
)
λ
2
Fit #2
— Specimen fit
Shannon / Cauchy
n
n
=
1.6059
V
D
=
86.5
n
400
450
500
550
600
650
700
750
1.600
1.605
1.610
1.615
1.620
n
2
=
1
+
0.6469
(
λ
2
−
0.007265
)
λ
2
Absorption Specimens
LED
SUN
I
F
Montebrasite
Brazil
LED
SUN
I
F
Montebrasite
Brazil, Paraíba State, Cuité