There is no direct import option between Facebook and Gmail. The entire Facebook contacts can be imported to Gmail using a simple trick. Here is how...
To import Facebook contacts to Gmail, you need a Yahoo account.
First Login to Yahoo mail, Then go to Contacts, then take import option. Select Facebook. Enter your Login details. Yahoo will import your Facebook contacts.
After completing import, select Actions > Export all > Select vCard single file. Enter the Captcha to download the file.
After saving the file, go to Gmail contacts > More > Import > Select file. Your are done. There would be duplicate contacts in your Gmail. Go to More > Find & Merge duplicate contacts to merge duplicates.