Of the c. 1,000 species of wattle in Australia, this is the only one with purple flowers (most are yellow or gold or cream).
It has two additional, more dubious distinctions. Firstly, it is unusually delicate and sparse-flowering for a wattle, most species being notable for their robust shrub or tree form and mass-flowering. Purple-flowered Wattle is a sparse sub-shrub often no more than 30 cm tall, and the photo depicts almost as many flower-heads on one plant as I’ve seen.
Secondly, it is extremely rare, being officially listed as Critically Endangered and reported from ten populations, totalling 500 individuals, in woodlands in a tiny area not far from my home town in far north Queensland. However, there’s somewhat more out there. A botanical friend knows of about ten additional populations and we’re about to undertake a comprehensive population count of these.