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I recently found this mineral crystallised within quartz at a rock crushing plant. Because of this I have no idea where this rock came from as material is transported to the site from a variety of locations. The mineral has a metallic lustre and is dark red / black. It is difficult to determine the crystals' structure because they are broken but a little is still intact and I guess that it is long and hexagonal. I have determined the hardness to be between 5 and 7. I appreciate that the pictures I have provided aren't great but it was difficult to photograph because of the sample being so small. If you want any pictures retaken I will be happy to do so.

 Close up if mineral. Scale is centimetres.

Image of rock. The mineral has formed in the quartz.

Another smaller crystal if the same mineral. Looks like it may be cubic but corner is broken so it is hard to say.

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  • $\begingroup$ i give you a upvote for giving a scale and for trying to describe the details of the rocks. $\endgroup$ – trond hansen Apr 29 '17 at 9:59
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Looks like rutile. Commonly associated with quartz, it's a simple titanium dioxide, though less commonly red in color. Nicely posted question, BTW.

enter image description here enter image description here

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My guess is your rock might contain huebnerite. It is brown-ish red to red in color. It is a vein forming mineral and I've seen examples similar to your specimen in metamorphic rock matrix cut by quartz veins. It has a similar tabular crystal shape.

enter image description here

Mindat reference.

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  • $\begingroup$ I performed another hardness test and determined that the mineral's hardness was less than 5.5, fitting the description of hübnerite. $\endgroup$ – The Garage Chemist May 5 '17 at 19:15

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