You are here:

Geology/what kind of rock is this?


shiny rocks
shiny rocks  
These rocks were found in a sea can shipping container in abbotsford B.C. Canada. They are very heavy for their size and very rough. The bigger one with indents looks like it has metal fibers in it. We would like to know what kind of rock it is or where we should go to find out.

Thank you

Hi Amber,
I think I can tell what you have there.  It looks like a metallic slag.  That's the waste product left over after the smelting process.  Itís the undesired impurities in the metals, which float to the top during the smelting process.  The metals start to oxidize as they are smelted, and slag forms a crust of oxides on the top of the metal being smelted. When the smelting is completed, the slag is skimmed from the top of the mix and disposed of.

Slag can be glassy or metallic, dull or shiny, silvery or gray to black.  It all depends on what the original ore was and what kind of smelting process was used. Slag is commonly composed of oxides of silicon, aluminum, magnesium, and sulfur.  Depending on the type of smelting process, it may also contain phosphorous, calcium, and ash.  These can be remnants of flux materials, such as limestone used in the process, or chemical reactions between the metal and the furnace lining.

Your specimens look like a metallic silicate slag.  I have seen many examples from all over the United States.  It is very useful and can be found in road and train track ballast, brick and mortar, cement, glass, phosphate fertilizer, or even jewelry.

I have been unable to find many images on the Net that display specimens like yours to good advantage but if you navigate to these sites you'll see an image that looks much like your samples:

Hope this helps.


All Answers

Answers by Expert:

Ask Experts


C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

©2016 All rights reserved.