Need Help Identifying A Rock

[Water_Gremlin]

Found two of these in a South Central Alaska creek bed. They struck me as an odd rock for the area and I brought them home. The one in the picture is almost the size of a basketball and fairly heavy. Any ideas?

 

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[omurcelik]

hi as far as i see, outer space is tuffaceous and if i see true inside a quartz nodule or inclusions and heavy metal enrichments likely silver or lead ....

 

[Water_Gremlin]

omurcelik, thank you for the response.

On another forum someone mentioned it could be a druzy chalcedony geode. I assume that is very similar to a quartz nodule?

From the pictures I have looked at I believe you are correct in saying the outter surface is tuffaceous. A few have told me its a pumice rock but this piece is far to heavy to be pumice.

Is there any value to pieces of this size? Just curious. The largest piece we found was 24" x 12" x 8" and probably 60 lbs if not more. The black spots are silt deposits from the river bed in which I found it.

 

[BurntBear]

Not Chalcedony from what I can tell. It looks like a carbonate mineral; maybe Dolomite or something along those lines.

 

[rock]

knock a piece off and see what is inside

 

[MrLee]

knock a piece off and see what is inside

Spoken like a true rockhound!