I know it's impossible for anyone to identify anything from a picture, but I was hoping to get some possible explanations and maybe some peace of mind from you all.

I have had to enter my crawl space in Colorado a few times over the past year. We recently bought a 1986 house in the Denver area. When I get in there, I have noticed small groupings of these white crystal formations on the ground. Obviously my mind jumps to the "a-word that shall not be named", but after reading many comments and some literature, I'm a little more skeptical. We have had some settling issues, and I'm guessing it's from water holding in the crawl space. So my gut instinct is efflorescence, but I haven't come across pictures of it as crystals this big. Does anyone have some insight that they could share with me? I'd gladly appreciate it!

white crystal I scooped with some metal

  • 2
    Looks like fiberglass cloth or stuff from old bags made from plastic weave.
    – crip659
    Commented Nov 25, 2023 at 19:42
  • I agree, that looks like fiberglass and is not related to any moisture issue.
    – RMDman
    Commented Nov 25, 2023 at 20:48
  • Gotcha. There is fiberglass insulation in there (I believe). Would it fall out from that? Or like crip said be from fiberglass cloth?
    – Jake K
    Commented Nov 25, 2023 at 21:02

1 Answer 1


As mentioned, it looks like fiberglass. Just use duct tape or similar to enclose it. There is no danger from such a small amount, but the tape will stop it from falling out.

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