I keep it on my back porch where it gets bright light, but no direct sunlight. When we get a blowing rain, the container does get a little wet.
What's interesting is that the moss that's outside lives in the shade and gets a lot of water (we've had tons of rain lately), and it does not have this white 'frost' on it.
I have no idea what type of moss it is, but it's very compact, and bright green when it it gets shade and plenty of water.
If it makes any difference, I've read that patches of moss are made up of thousands of tiny plants that get there nutrients from the air and water, and do not need soil. When I got it from its natural habitat, it came up with some sandy soil, less than 1/4" thick. I placed it directly on the potting mix in my container.
Any ideas on what this could be? I can post a picture if need be.
Thanks for any and all help!

Julie