Custom price type attribute is not working in Layered navigtion

[nimita]

Hello ,
I have some issues in layer navigation with price type attribute.
I have created attribute named 'metal_weight' with 'price' type. and set this attribute visible in layered navigation.
I have set metal weight  0.5gm to 50gm in products.
Now in front-end layer navigation , metal weight is displayed with single filter option '$0.00 - $0.00 (8)'.
while it should be display like price option range because I have set attribute type price.
Is there any solution to display range type attribute in layer navigation
I don't want any third party extension.