What is the composition and origin of this rock found in Israel?

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In summary, the conversation is about a rock found in Israel that appears to be a "hammerstone" or pounder. It is believed to have been used as a tool due to pecking on the bottom side. The rock is 11 cm high and 13 cm wide and has likely cracked from heat exposure. The discussion also includes suggestions for further analysis, such as looking at the inside of the rock and testing for magnetic properties. The red areas on the rock could be due to iron oxide caused by weathering.
  • #1
wilhen
https://drive.google.com/file/d/0B6vFDqtp6QNEOW9CeUFYOWRGczA/view?usp=sharing The pictures in this post are of a "hammerstone," or pounder. It was found next to a large lower grinder (metate, quern, whatever term you prefer). It is 11 cm high and 13 cm wide. It most likely cracked from heat exposure incident to the destruction of the house it was found in. The site is located between Tel Aviv and Jerusalem, Israel. A friend suggested it might be granite and the red areas exposed from the chipped cortex might be k-feldspar. I was wondering if you had other suggestions.
https://drive.google.com/open?id=0B6vFDqtp6QNEOW9CeUFYOWRGczA
https://drive.google.com/open?id=0B6vFDqtp6QNEUzJVMG9Gd1FPSzQ
 
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  • #2
Some points:
This has an accession number on it so you have to treat it carefully.

Showing the inside of the rock ball will help - the weathered rind is not very enlightening. The cracks appear to allow a full cross-sectional view.

People do not want to lug large rocks around so the likelihood is that the rock is local or an accidental, so other specimens probably lurk in the locale. And you can have a mineralogist do destructive analysis on those other specimens if needed. e.g., acid tests or sections for microscopy.

If the shape is not man-made then it implies alluvial processes were at work - like violent stream flows or glaciation.
 
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  • #3
Just a hunch - but is it magnetic ?
 
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  • #4
jim mcnamara said:
Some points:
This has an accession number on it so you have to treat it carefully.

Showing the inside of the rock ball will help - the weathered rind is not very enlightening. The cracks appear to allow a full cross-sectional view.

People do not want to lug large rocks around so the likelihood is that the rock is local or an accidental, so other specimens probably lurk in the locale. And you can have a mineralogist do destructive analysis on those other specimens if needed. e.g., acid tests or sections for microscopy.

If the shape is not man-made then it implies alluvial processes were at work - like violent stream flows or glaciation.
Thanks, Jim. The site directors gave me permission to research this piece, and without specific context I thought it would be safe to put on a forum. Unfortunately, I didn't get a picture of the rock interior. We're confident the rock is a tool because of pecking on the bottom side, not shown in the photographs.
 
  • #5
Nidum said:
Just a hunch - but is it magnetic ?
I don't know. I never placed a magnet near it.
 
  • #6
The fractured surface of the rock looks to me a bit like a quartzite.

If you look closely at the bottom of pix 1 you will see some lines or curves that appear to be variations in the rock. I suspect they were fossil shell CaCO3 fragments that were dissolved in the metamorphic process by silicic acid, then replaced with silica.

The parallel cracks suggest either historical weaknesses due to bedding, or unloading cracks formed during uplift and approach to the surface.

Rotate the rock near a magnetic compass to see if magnetic material is present. Red iron oxide haematite is not magnetic, black magnetite is magnetic.

The red surface may be iron oxide produced by weathering in the soil. It appears to have stained the cracks in the rock and the weathered crust.

Maybe the rock was used to prepare red ochre and retained some material.
 

1. What is the composition of the granite like rock?

The composition of this rock is primarily made up of quartz, feldspar, and mica.

2. How can I identify this rock as granite?

Granite can be identified by its coarse-grained texture, often with visible crystals of different colors, and its hardness on the Mohs scale of 6-7.

3. Is this rock formed through igneous or metamorphic processes?

Granite is typically formed through igneous processes, specifically the slow cooling and solidification of molten magma deep within the Earth's crust.

4. What are some common uses for this type of rock?

Granite is commonly used in construction as a building and decorative material, as well as in countertops and monuments.

5. Can this rock have variations in its appearance and composition?

Yes, there can be variations in the appearance and composition of granite depending on its geographic location and the specific minerals present in the magma during its formation.

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