TIL that Commander One Pro app can be used to mount an Android phone or tablet to a Mac for file transfer purposes. That app retails for US $30, I picked it up in a special promotion in Dec 2015 for US $2.
When used with my Lenovo Tab 7 Essential, it shows the micro SD card that's mounted in the external slot. This is a 16 GB card, it can take a 128 GB card if needed.