Most common among Mimosaceae along with Vilaiti Keekar (Prosopis juliflora) & Jhand (Prosopis cineraria) in Hodal, Distt. Faridabad, Haryana & between Hodal & Delhi. It is unmistakable when in flowers with very long paired white spines. Leaves are twice feathered with 3-6 side-stalks. Fruits are greyish beaded pods (not in pictures) & unmistakable for Id.
Acacia nilotica is a tree 5-20 m high with a dense spheric
crown, stems and branches usually dark to black coloured, fissured bark, grey-pinkish slash, exuding a reddish low quality gum. The tree has thin, straight, light, grey spines in axillary pairs, usually in 3 to 12 pairs, 5 to
7.5 cm long in young trees, mature trees commonly without thorns. The leaves are bipinnate, with 3-6 pairs of pinnulae and 10-30 pairs of leaflets each, tomentose, rachis with a gland at the bottom of the last.
Above details taken from Wikipedia link below:
Another good link is given below for more details: