Lost Mothers Records

I have a friend who is trying to trace his mothers heritage. Unfortunately her name has been changed. I have a birth certificate of a child born to her Jomatten
Sibosach born 11 Oct 1893 at Marble Bar, Western Australia. His mothers name is recorded as Chonah no maiden name. The Fathers surname has Sibosach address is Cossack Western Australiabhis, ocupation reads Diver. which makes him at that stage a pearl diver.

Can some one help me find these people? I have been told they may be from Thursday Island or Philippines

Regards

Noelene Lee