BATU or ROCK ISLANDS (Dutch Batoe), three greater and 48 lesser islands, Dutch East Indies, W. of Sumatra, between o° 1o' N. to o° 45' S. and 97° 50'-98° 35' E., belonging to the Ayerbangi district of the lowlands of Padang (Sumatra). They are separated by the strait of Sibirut from the Mentawi group. The three chief islands, from N. to S., are Pini or Mintao, Masa, and Bala; land area 445sq.m. The islands are generally low, and covered with forest, in which the coconut palm is conspicu ous. There is trade in copra, oil, and other forest produce. The natives, about 3,000 in number, are of Malayan or pre-Malayan stock, akin to those of the island of Nias to the N.W. Only about 20 of the smaller islands are inhabited.