According to HansPeter Vietze Chandmani means Jewel or precious thing However I am still not sure wether in this case Chandmani Uul is a toponym nor not There seems to be a Chandmani uul near Ulaangom source a picture book about Uvs by G Tsatsralt or similar Uul Us Nutag or similar UB  but it didnt look very big on the picture Of course that doesnt mean it cant be significant for other reasons  Baabar uses the genitive forms in Mongolchuud Nuudel Suudal paperback UB  vol Togloomyn Bugd Nairamdakh Ulsp end of chapter  The other Aimags given are Khan Tashir Uulyn Tsetserleg Mandal Uulyn Bogd Khan Uulyn Khan Khentii Uulyn aimag At least the latter two seem to be named after real mountains