Identifying and restoring old stone

[malaverdiere]

Hi everybody!

This old sharpening stone is from my late father. At least 20 years old, possibly more. It is a dark grey, rough on some spots and smooth in others and has the shape of a scythe stone. It was always used with oil.
Some rust is showing, and I'm not seeing any logos or brands of any kind.

Anybody can tell what it would be made of? And how to make it like new?
Based on what I have learned on this forum, the color hints at silicon carbide or aluminium oxide. I was thinking of scrubbing it using mineral oil and a rough non-metal brush to clean it up.

 

[kvaughn]

I've had one of those for years. I use it to sharpen my machetes. I clean mine with dish soap, hot water and a brush when it gets matted/slick. I think mineral oil might clog it.--KV

 

[captjlw]

I've always had very good results scrubbing with dawn and water with a green 3M pad then scrubbing again with barkeepers friend powdered cleaner & polish.