Is their any system table or way to find out what column/columns are used to make index/ key ?

I tried this but it does not give the columns !!
SQLWKS> select * from user_indexes
2> where TABLE_NAME in ('MWEBAUTH', 'MWEBMATRIX')
3> order by table_name

INDEX_NAME TABLE_NAME
------------------------------ ------------------------------
IX_AUTH_WORK MWEBAUTH
SYS_C0039449 MWEBAUTH
UK_AUTH_1 MWEBAUTH
IX_MAT_RES MWEBMATRIX
SYS_C0039476 MWEBMATRIX
UK_MATRIX_1 MWEBMATRIX

In other words I want to know col1, col2, col3..
ix_auth_work is on (col1, col2, col3..) on table mwebauth

Thanks
Sonali