| General Formula: ZrSiO4 |
Sample: GB 12 | System: Tetragonal |
|---|---|---|
 |
 |
 |
| Zircon Euhedral zircon grain within a granitic gneiss. Note the highly fractured nature of the grain and the very strong relief. Field of View 1 mm, plane light |
Zircon The same image as that on the left, the high interference colours of the zircon grain are not readily evident in this image, Field of View 1 mm, crossed polars |
Block diagram showing the relationship between the crystallographic axes and the indicatrix axes. |
Optical Properties
| Colour Pleochroism |
colourless to pale brown weakly pleochroic |
Form | euhedral to sudhedral tetragonal crystals with pyramidal terminations |
| Relief RI |
very high positive nw = 1.920-1.960 ne = 1.967-2.015 |
Cleavage | not usually seen in thin section |
| Birefringence Interference Colours |
0.036-0.065 up to third or fourth order |
Twinning | not twinned |
| Interference Figure Optic Sign 2V |
uniaxial positive |
Optic Orientation | elongate grains are length slow with parallel extinction |
| Composition | significant Hf for Zr and minor U and Th | Alteration | does not readily alter |
| Occurrence | common accessory mineral in felsic rocks and less common in mafic rocks, common in metamorphic rocks derived from clastic sediments, common detritial mineral | Distinguishing Features | small, high-relief grains with bright interference colours |
