1. Sedimentary Rocks

2. Clastic vs. Non-clastic
Sedimentary rocks in two major groups
Clastic (detrital)
Composed of fragments of silicate minerals (mostly quartz and clay)
Name largely determined by the grain size (see handout)
Non-clastic
Composed of various minerals (usually just one)
Name largely determined by the composition

3. Clastic (detrital) Coarse grained (> 2 mm)
Conglomerate (rounded pieces)
Breccia (angular pieces)
Medium grained (<2 mm but still visible)
Quartz sandstone (mostly quartz)
Arkose (abundant feldspar – often pink)
Greywacke (much clay – often dark in colour)
Fine grained rocks (cannot see ind. grains)
All “mudrocks”
Siltstone (gritty), shale (splits easily), claystone (smooth, slippery feel)

4. Non-clastic All one mineral (usually)
Often “crystalline” (visibly so or VERY smooth (with conchoidal fracture)
Named according to mineral present (use hardness and reactivity to HCl)
H > glass, no HCl reaction: mineral is chalcedony, rock is chert
H ~ penny, no HCl reaction: mineral is dolomite, rock is limestone (dolomitic)
H ~ penny, HCl reaction: mineral is calcite, rock is limestone
Penny > H > fingernail, salty taste, no HCl reaction: mineral is halite, rock is Rock salt
H < fingernail, no HCl reaction: mineral is gypsum, rock is Rock gypsum

5. Doing the lab – CaCO3? Test with HCl (acid).
Fizz means calcite present.
If it’s all calcite – rock is non-clastic
Be careful to note if the rock is dominantly calcite or just partly (i.e., is the rock all calcite, a limestone, or just random parts, e.g., a calcite cemented sandstone)

6. Doing the lab – C or NC
C: is the rock clastic; i.e., composed of discrete particles (grains) of silicate material (quartz, feldspar, clays, etc.)?
NC: is the rock non-clastic; i.e., all one mineral, probably a non-silicate, and probably crystalline?

7. Doing the lab – Grain size
Only applicable to clastic rocks (i.e. with non-clastic rocks say “not applicable” or “n.a.”)
Coarse grained (c.g.): > 2 mm
Medium grained (m.g.): vis. grains to 2 mm
Fine grained (f.g.): gritty on teeth
Very fine grained (v.f.g.): slippery to feel (probably with an earthy smell)
HINT: The higher the clay content of clastic rock the darker the colour.

8. Doing the lab – Components
What makes up the rock
Grains? (Sand, silt, pebbles, …)
Of what?
A single mineral?
Multiple components? …

9. Sorting
Only applicable to clastic rocks (for non-clastic rocks say “n.a.”)
Fine-grained (and v.f.g.) rocks are too fine to see the sorting. Say “too fine to see” or “n.d.”
Two kinds of sorting
Compositional
Well = composed of only one component
Poor = mix of several different components
Size
Well = all grains are same size
Poor = grains are all sizes
Compositional and Size sorting usually go hand-in-hand

11. Other features Include: Fossils Salty taste
Obvious bedding/laminations
Ooids (oolites) …

13. Name
Use
Handout chart
Book
Wall poster

15. Questions?