Does a metal being "soft" equal being able to scrape onto paper?

When you scrape aluminum onto paper, it makes a faint mark. The question is, does softness of a metal correlate to how well a mark shows up when you scrape it onto a surface such as paper?




«How well a mark shows up» is an ambiguous description. Yet,


* *Does softness of a metal correlate to how easy material abrades?* If you refer to [Mohs' scale](https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness), yes. Modern test kits contain pens with synthetic alloys to offer reproducible access to Mohs' levels of hardness


[![enter image description here](https://i.stack.imgur.com/Ha4Tt.png)](https://i.stack.imgur.com/Ha4Tt.png)


([credit, commercial source](https://www.mineralab.com/MohsHardnessIndustrial/))


like it is mostly known in art for silver, the [silverpoint](https://en.wikipedia.org/wiki/Silverpoint). Though similar to silver in Mohs' scale, I didn't hear (so far) about an aluminium point. It equally is one of the techniques in geology, to compare the colour of the mineral *as such* with the colour of the streak of this mineral e.g., on a white tile you carry with you in the field; the two needn't be equal.
* *Is the trace of the material visually discernible from the paper?* This depends on the paper. Paper often is sold bleached and containing fillers (e.g., $\ce{CaCO3}$, $\ce{TiO2}$) for a white appearance. Again returning to art, your paper may be darker from the get-go, then allowing to use the technique known as [trois crayons](https://en.wikipedia.org/wiki/Trois_crayons) to introduce heights and lows with pencils used:


[![enter image description here](https://i.stack.imgur.com/P8VRi.jpg)](https://i.stack.imgur.com/P8VRi.jpg)


(example of a *trois crayons*, credit [Wikipedia](https://en.wikipedia.org/wiki/Trois_crayons))
* *Does the trace adhere well to the paper?* Like e.g., for charcoal, pen, chalk, in part this depends on the roughness of the paper if small particles enter grooves of the substrate. Often, the adhesion to the substrate is enhanced after drawing by applying a coating called [fixative](https://en.wikipedia.org/wiki/Fixative_(drawing)). (Hair-fixing spray sometimes is a cheaper alternative.)


In case of aluminum, you may bet that its metallic reflectance stays; on surface, it will oxidize to transparent, colourless $\ce{Al2O3}$. In case of e.g., silver, this is going to get dark (think $\ce{Ag2S}$).


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