What on earth is this?

[Mfb]

Hi every one! 

A family member passer away recently and we are in the proces of sorting out their belongings. I found this rock. It looks really cool, is about a fist in size and weighs about 1.2kg (estimate). Can anyone help identify it? 

Best wishes

Morten

Here is another one

[QuantumT]

Have you tested to see if it's magnetic? If it is, it's probably just iron.

[Strange]

I'm going to guess pyrites, from my limited knowledge of rocks.

[Mfb]

Good question! I actually did, it is not magnetic

 

[Sensei]

1 hour ago, Mfb said:

A family member passer away recently and we are in the proces of sorting out their belongings.

I am sorry to hear about your loss..

 

1 hour ago, Mfb said:

Can anyone help identify it?  

Did you try to cut a small piece of it, couple mm, and put it in e.g. acetic acid and citric acid.. ? Do you have some strong acids like hydrochloric acid, sulfuric acid, nitric acid?

Yet another basic test is flame test. Cut small piece and put it in flame and make photo. What color has flame?

 

Edited March 4, 2019 by Sensei

[swansont]

4 hours ago, Mfb said:

Hi every one! 

A family member passer away recently and we are in the proces of sorting out their belongings. I found this rock. It looks really cool, is about a fist in size and weighs about 1.2kg (estimate). Can anyone help identify it? 

 

Fist size implies a radius of 4-5 cm for a sphere, so the volume is of order 100 cm^3, putting the density near 10 g/cm^3  (see below)

(Having a more precise measure of this would help quite a bit)

That eliminates a lot of suspects.
https://www.engineeringtoolbox.com/mineral-density-d_1555.html

I was thinking galena, owing to the color and lack of magnetism, but the crystal structure is not really consistent with samples I have seen (but I'm not a geologist). You can sort the above list by density, and check out the candidates near 10 g/cm^3. Better yet would be to make a more precise measurement and then look at the candidates.

 

 

[Sensei]

1 hour ago, swansont said:

Better yet would be to make a more precise measurement and then look at the candidates. 

That's essential operation. Measure mass and volume and calculate density.

1 hour ago, swansont said:

Fist size implies a radius of 4-5 cm for a sphere, so the volume is of order 100 cm^3, putting the density near 10 g/cm^3 

4/3 * PI * 4^3 = ~268 cm^3

4/3 * PI * 5^3 = ~524 cm^3

I just filled beaker with water (up to 500 mL), and put my (not so big) fist inside, and it was 320 cm^3 (read 820 mL on the scale).

 

[swansont]

45 minutes ago, Sensei said:

That's essential operation. Measure mass and volume and calculate density.

4/3 * PI * 4^3 = ~268 cm^3

4/3 * PI * 5^3 = ~524 cm^3

I just filled beaker with water (up to 500 mL), and put my (not so big) fist inside, and it was 320 cm^3 (read 820 mL on the scale).

 

Doing the math in my head. Forgot to multiply by 4.

That, of course, changes the above density analysis by a lot.

[Intrigued]

Molybdenite is a possibility. If it feels soft and greasy and leaves a blue grey streak on a white ceramic surface that's it. Galena, as swansont suggested, is possible, except that doesn't look like a cubic crystal structre.

[Aly]

The rock you are trying to explain is called Molybdenite. It is supposed to leave a blueish gray streak and is the color of gray. It also is greasy and has a soft surface.