I'm hoping others can help me identify this odd looking hollow rock/mineral/metal thing. I'll give pictures, then a video, then some other helpful info.
The streak is reddish. I'm colorblind, so can't give more info, but I can provide a photo. The center streaks are from the unknown rock. The upper ones are from sulphur and the lower ones are from pyrite:
The outer surface is interesting. It's spiral-like. Here's a video that shows the overall shape a bit better than pictures can:
- Video showing overall shape <--- Pretty helpful
Here's additional useful info.
Specific gravity (measured by me): Somewhere between 3.30 and 3.46. Upon exposing a new surface, I noticed a few air pockets. You can see them in the photo above if you look closely. No idea how much this decreases the S.G. measurement.
Location found: On the surface of a currently-empty stream bed. (It's been a dry summer.) The stream is in a wooded area in McCollum Park in Everett, WA. However, there is casual foot traffic from the city, so it's not necessarily a native rock. Could have been brought in. There are also buildings nearby.
Other useless info about discovery: The hollow inside part was full of some dirt and fibrous material.
Magnetic interactions: Attracted to magnet.
Mohs Hardness: Somewhere between 4 and 6 I think. It's rather brittle, so I find it difficult to do the test definitively.
Similar to: Looks very similar to my hand sample of "magnetite". The S.G. is all wrong to be pure magnetite (I'm new to this, bear with me), but it's still pretty similar to my sample.
Beyond knowing what the mineral actually is, I'd like to learn the process of how such a strange shape can be formed. Crossing my fingers for a natural explanation rather than some artificial building/construction explanation.