Quartz is one of the most common minerals in the Earth's continental crust. The most important
<br>
distinction between types of quartz is that of macrocrystalline (individual crystals visible to 
<br>
the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals 
<br>
visible only under high magnification). Major varieties:

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<table style="text-align:left;">
	<tr><td>Agate: </td><td width="10">&nbsp;</td><td>banded chalcedony, translucent</td></tr>
	<tr><td>Amethyst: </td><td width="10">&nbsp;</td><td>purple, transparent</td></tr>
	<tr><td>Aventurine: </td><td width="10">&nbsp;</td><td>translucent chalcedony with small inclusions (usually mica) that shimmer</td></tr>
	<tr><td>Carnelian: </td><td width="10">&nbsp;</td><td>reddish orange chalcedony, translucent</td></tr>
	<tr><td>Chalcedony: </td><td width="10">&nbsp;</td><td>any cryptocrystalline quartz, although generally only used for white or lightly colored material</td></tr>
	<tr><td>Citrine: </td><td width="10">&nbsp;</td><td>yellow to reddish orange, greenish yellow</td></tr>
	<tr><td>Jasper: </td><td width="10">&nbsp;</td><td>opaque chalcedony, impure</td></tr>
	<tr><td>Milk Quartz (Snow Quartz): </td><td width="10">&nbsp;</td><td>white, translucent to opaque</td></tr>
	<tr><td>Morion: </td><td width="10">&nbsp;</td><td>dark-brown, opaque</td></tr>
	<tr><td>Onyx: </td><td width="10">&nbsp;</td><td>agate where the bands are straight, parallel and consistent in size</td></tr>
	<tr><td>Prasiolite: </td><td width="10">&nbsp;</td><td>mint green, transparent</td></tr>
	<tr><td>Rock Crystal: </td><td width="10">&nbsp;</td><td>clear, colorless</td></tr>
	<tr><td>Rose Quartz (Pink Quartz): </td><td width="10">&nbsp;</td><td>pink, translucent</td></tr>
	<tr><td>Smoky Quartz: </td><td width="10">&nbsp;</td><td>gray or brown, transparent</td></tr>
	<tr><td>Tigereye: </td><td width="10">&nbsp;</td><td>fibrous quartz, exhibiting chatoyancy</td></tr>
</table>
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