grain of sand

[cmungall]

currently we have

[1] grain of desert sand is_a sand
[2] grain of desert sand is_a grain of sand

all 3 terms are undefined.

I propose:

* treat 'sand' as a mass noun synonym for 'portion of sand' and define it as such

• remove [1]
• retain [2]
• add <part_pf desert sand>

We also have:

[3] sand is_a rock

I propose we change to RO:derives_from

Original comment by: cmungall

[pbuttigieg]

This looks like it has been addressed. I agree with the edits made, except I think we should have desert sand 'has part' some `grain of desert sand' as one can't have the mass without the grains.

[cmungall]

On reflection there may be some naivety in my location-based classification. Isn't it the case that desert sand has different properties based on its exposure etc.