From finder you need to be in Pictures (not the application) and control-click on iPhoto Library.
iPhoto will have created duplicates and hidden your originals. LR has no face recognition built in. You need to find your masters from the iPhoto Library - Right-Click and select “Show Package Contents”
Older versions of iPhoto uses an Originals folder and in later versions; Masters. It’s not a good idea to go messing with the structure as it could corrupt the iPhoto Library. Apple has made this structure for good reason; so that you can always use the revert command to go back to an original, even if you have edited in iPhoto using cropping or red eye removal, for example.
However, if you have no further use for iPhoto, you could consider moving your originals/masters to a new folder structure (iPhoto automatically creates dated sub-folders) and then importing to Lightroom. Alternatively if you still need iPhoto, export duplicates to the desktop and bring those into Lightroom. That will keep iPhoto safe.
I do actually use iPhoto for creating events which can then be used to make cool slideshows within iPhoto. However Lightroom is my main management and photo editing tool and I have created an export pre-set for sending jpegs into iPhoto. I have even dragged the iPhoto Library off the hard drive to an external hard drive – but that means keeping it connected when using iPhoto.
This link has further information on folder locations for iPhoto:
Where iPhoto Pictures are Located and How to Access the iPhoto Library and Picture Files