Purple Australian Finger Lime, Citrus australasica var. sanguinea
This is the rare purple fruited form with leaves showing a purple hue as well, especially when young.
Tiny evergreen leaves on a spiny bush set this Australian native apart from the rest of Citrus.
The fruit is like a small gherkin in shape and filled with what has been described as Citrus Caviar which makes a satisfying pop when eaten.