Help With Identifying Dark Silver Shiny Crystal / Rock

[IronManoc]

Hi All,

Can someone provide me with some information about the rock/crystal in the image attached?

This rock/crystal is not attracted to magnets and is not detectable with a metal detector. 

The approximate dimensions are as follows: length 9.5cm, breadth 6.5cm and height 7.5cm.

It weighs about 490g which is pretty heavy for its size.

The main color is dark silver color and reflects green, blue and purple.

[Steve Herschbach]

Looks like slag, common near railroads and smelter locations.

https://albionfireandice.co.uk/what-is-slag-anyway/

https://en.wikipedia.org/wiki/Slag

Slag Photo Gallery

[IronManoc]

Hi Steve,

Thank you for the info.

What surprised me was that it is not detectable by a metal detector however with a diamond tester it 'rings'.

It is also extremely tough and with the streak test it does not mark anything.

Thank you again for the links.

[Steve Herschbach]

It's basically colored glass so no streak or conductivity. Other types, iron slags, might be real reactive with a detector. Some might even leave a streak. It just depends on what the original source material is that was being smelted.

[Geologyhound]

It looks a little like carborundum (silicon carbide).  Still industrial byproduct or discarded product, but it would explain the color and the hardness.

[IronManoc]

Hi Geologyhound,

Thank you for the info.

I have also checked online and it has similar patterns to Carborundum.

I have attached two images of the patterns. Please note that the tiny whitish grains are sand so they are not attached to the actual rock. 

Thank you again for the reply.