Length around 45-49mm, wingspan for male around 58mm and for female around 63mm; Hindwing around 24-36mm; Larva around 30-35mm.

The male has dark brown-black wingtips with blue veins. Immature insects often have much paler, browner wings. They have metallic blue-green bodies and blue-green eyes. The female has dark brown iridescent wings, a white patch near the tip of the wings and a metallic green body with a bronze tip of the abdomen.

Comparing with similiar family species Calopteryx splendens (Banded Demoiselle), the difference exists in extention of the band in the wing patch.  The wing patch of C. splendens starts at the nodus but can reach up to the wing-tip in southern races. The nodus is the sharp dip mid-way down the upper edge of the wing. That of the C. virgo, the colouring on the wing starts before the nodus, further towards the body, than the Banded demoiselle.

Demoiselles are damselflies that belong to the family group called "Calopterygidae". This family includes two large damselfly species: the Banded Demoiselle Calopteryx splendens and the Beautiful Demoiselle Calopteryx virgo. Demoiselles have a graceful butterfly-like fluttering flight and are usually seen flying over riverside vegetation.

Preferred environment includes upland and lowland unpolluted lotic sites especially with wooded banks and of moderate flow with sandy and gravely beds. Restricted to faster running clear water, found only along streams and rivers, often acidic, with sand or gravel bottom. Mostly found along heathland or moorland streams, though can also occur in farmland and woodland, including well shaded streams. Prefers cooler water than Banded Demoiselle. As streams broaden this species gives way to Banded Demoiselle, where there may be a broad overlap. Occasional hybridisation may take place. Sensitive to waterway management (clearance of vegetation) and pollution.