Slag is the glass-like by-product left over after a desired metal has been separated (i.e., smelted) from its raw ore. Slag is usually a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals. While slags are generally used to remove waste in metal smelting, they can also serve other purposes, such as assisting in the temperature control of the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.

[Wiki](https://en.wikipedia.org/wiki/Slag)

[Slag Glass  from the Glass Encyclopedia](https://www.glassencyclopedia.com/slagglass.html)

[Furnace slag](https://www.google.com/search?q=furnace+slag&tbm=isch)

[Cullet glass](https://www.google.com/search?q=cullet+glass&tbm=isch)

[Andara crystals/rocks](https://www.google.com/search?q=andara+crystal&tbm=isch)

[Iron oxide nodules](https://www.google.com/search?q=iron+oxide+nodules&tbm=isch) (not slag)

[Limonite](https://www.google.com/search?q=limonite&tbm=isch) (not slag)

[Tektite](https://www.google.com/search?q=tektite&tbm=isch) (not slag)

[Indochinite](https://www.google.com/search?q=indochinite&tbm=isch)(not slag)

[Ferrochrome](https://www.google.com/search?q=ferrochrome&tbm=isch) (not slag)

[Anthracite](https://www.google.com/search?q=anthracite&tbm=isch)(not slag)

[Bitumen](https://www.google.com/search?q=natural+bitumen&tbm=isch) (not slag)

[Cuprite](https://www.google.com/search?q=cuprite&tbm=isch) (not slag)

[Flint (white crust)](https://www.google.com/search?q=flint+white+crust&tbm=isch) (not slag)

[Some Meteorite Information](https://sites.wustl.edu/meteoritesite/items/slag/)

[I think I found a meteorite. How can I tell for sure?](https://www.usgs.gov/faqs/i-think-i-found-meteorite-how-can-i-tell-sure)

r/itsslag