Chalcedony also
known as Cryptocrystalline Quartz
Mineral Group: SILICATES
RocksForKids.com
| Chalcedony is always opaque or
tranlucent and never transparent. It comes in many colors and forms. Chalcedony is a cryptocrystalline quartz. It has crystals so small that a microscope is needed to see the crystal structure. The following are some of the common semi-precious gemstones that are cryptocrystalline quartz.
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Chalcedony
The hollow spherical geode section is partially filled in on the inside with smooth, beige, small botryoidal chalcedony. It looks like rounded gray peas. |
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 Chalcedony is often
found in geodes. Its crystal habit, or growth pattern is often
botryoidal. |
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Bloodstone or
Heliotrope
Bloodstone got its name because the red spots caused by iron oxides look like drops of blood as they appear on a dark green background. |
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Jasper
This creamy yellow-orange, hard jasper nodule shows its waxy luster in areas where the rough “skin” has been broken off. It is translucent when sliced thin but opaque when in a large chunk. |
 SPECIMEN ORIGIN: Lake Superior, Ontario, CANADA The bright red of jasper makes it easy to identify. This specimen is dramatically layered. It has 2 flat, cut surfaces with a slight polish.
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 SPECIMEN ORIGIN: Nova Scotia, CANADA This smooth, blocky, opaque beach pebble has reddish brown jasper sandwiched between layers of other rocks.
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Chert
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 This very hard striped rock is found in nodules or lenses in limestone. It takes a very high polish and was used by First Nation people in southern Ontario to make pipes with. |
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