Black Slate & Quartzite Falls
As you might guess from their names, the lithologies of these two falls are slate and quartzite, respectively. I decided to lump these two falls together since they're only about 900 ft apart from one another. Though neither of these falls are significantly large, the surrounding coniferous woodlands make these falls (particularly Quartzite Falls) awesome spots for camping due to the sparse ground vegetation. If you decide to camp here (especially in the spring), make sure to bring bug spray or the mosquitoes will carry you away.
The woods are generally clear enough that you can hike the riverbank up the river. There is a logging road on the east side of the Slate River that runs relatively parallel to it if you'd rather not bushwhack it. Additionally, a stretch of Arvon Road gets pretty close to the Upper Black Slate Falls.
If you've got a 4x4, there is also an abandoned slate quarry a little ways southwest of the falls that might be worth checking out if you've got time. I've never been there myself but Jacob Emerick details this place here. If you do decide to check it out, make sure you're prepared to get stuck. In the spring the logging trail that leads here is extremely mucky and may be impassible at times.
To get here from Houghton, head south towards Marquette on US-41. As you're coming into L'Anse, turn left by Burger King onto L'Anse Ave. Continue 1000 ft and turn left onto E. Broad Street. Continue 2000 ft and turn right onto N. Main Street. Continue for 11.5 miles and turn right onto Arvon Road. Drive 3.4 miles and turn left onto All Wood Road. Note that it may be unmarked. Drive over the bridge and immediately park in one of the bare areas on the side of the road.
Big thanks to Andrew Dubay for the pictures!