Quartz

Crystalline

>20 µm

~0 wt.%

Fine-quartz

Granular

5 - 20 µm

<1 wt.%

Chalcedony

Parabolic fiber bundles

<100 µm length

1 - 2 wt.%

Crypto-crystalline

Poorly defined

1 - 10 wt.%