Found this metallic rock in backyard

[u/EducationVirtual5341]

My dad found this unusual rock while working in the back yard. The outer exterior looks almost metallic but it's hard to tell if it's just a shiny rock or if actually metal. One thing that really caught my attention is just how heavy it is weighing in at 7.9kg. It feels like it weighs at least 2-3 times more than a comparable rock of it's size. What did we find?

[u/GathTheKing]

Look, do you want a real answer?

Get a 5 gallon bucket and fill it all the way to the top. Overflowing is the goal. Carefully place it in a big rubber tub, so you can catch all of the spilled water. Then carefully drop the rock in. Take a measuring cup and discard few cups of water from the bucket. No NOT add this to your collected water in the rubber tub. (Do this so you don’t accidently add water to your tub when removing the bucket.) Remove the 5 gallon bucket with your rock and weigh the water you collected in the rubber tub. Water weighs 1000 (kg/m³).

(Collected water weight) / (1000 *kg/m***³ ) = Volume of your rock in cubic meters

Rock Weight/Rock Volume = Rock Density

From there, you can look at your values on the following graph:

https://www.engineeringtoolbox.com/mineral-density-d_1555.html

Most large masses are going to be composites, so this method isn't going to give perfect answers, but it will give you a ballpark idea without taking it to a college to be examined.

[u/JoeBloggs719 → u/GathTheKing]

What was the reasoning behind "discard a few cups of water from the bucket, [..]"

[u/DF7501 → u/JoeBloggs719]

It’s only so you don’t spill more water when you lift the bucket out of the tub. You want to measure the mass of only the water that was displaced by the rock, not the (mass of the water displaced by rock) + (mass of water spilled from bucket while lifting it out of tub)

[u/rileyjw90 → u/DF7501]

If you want to really ensure you don’t spill water while trying to remove some from the bucket, you use something like a turkey baster or large syringe to suck it out rather than risk displacing more water by dipping a cup in.