Are proceeds from the sale of bullion income for tax purposes?

Are proceeds from the sale of bullion income for tax purposes? Please read what the IRD has to say about it: https://www.taxtechnical.ird.govt.nz/-/media/project/ir/tt/pdfs/questions-we-ve-been-asked/2017/qb17008.pdf?la=en
$259.26/gm
$5,184.55/kg