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nm. microlith, microscopic crystal

(n.)
A rare mineral of resinous luster and high specific gravity. It is a tantalate of calcium, and occurs in octahedral crystals usually very minute.
  

(n.)
A minute inclosed crystal, often observed when minerals or rocks are examined in thin sections under the microscope.
  

General Information:
 Chemical Formula:
(Na,Ca)2Ta2O6(O,OH,F)
 Composition:
(Molecular Weight = 529.02 gm)
Sodium 6.52 % Na
Calcium 3.79 % Ca
Tantalum 68.41 % Ta
Hydrogen 0.06 % H 
Oxygen 20.87 % O 
Fluorine 0.36 % F 
 Empirical Formula:
Na1.5Ca0.5Ta2O6.6(OH)0.3F0.1
 Environment:
Granitic rocks.
 IMA Status:
Approved IMA 1977
 Locality:
Isalnd of Uto, State of Stockholm, Sweden.
 Name Origin:
From the Greek mikros - "small" and lithos - "stone."
Physical Properties:
 Cleavage:
[111] Indistinct, [111] Indistinct, [111] Indistinct
 Color:
yellowish brown, reddish brown, greenish brown, green, or gray.
 Density:
4.2 - 6.4, Average = 5.3
 Diaphaniety:
Subtranslucent to opaque
 Habits:
Disseminated - Occurs in small, distinct particles dispersed in matrix., Pseudo Octohedral - Crystals show an octohedral outline.,
 Hardness:
5-5.5 - Apatite-Knife Blade
 Luminescence:
None.
 Luster:
Vitreous - Resinous
 Streak:
light yellow
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