Help with Identification.

[SneakyCuttlefish]

I would say either tourmaline (schorl) or rutile. Crack a piece of and get a specific gravity.

 

[Ditch]

Thanks for everyones feedback in helping to identify this specimen. Trying to work out what it is just from photographs is difficult, I have looked at many different websites & it is hard to tell what it is based on just looking at pictures. In the images I posted the crystals look to have a blue hue to them, but in natural light they are definitely black. Your suggestions of other minerals it could be helped in narrowing down what it might be.

What I have found out by reading those articles & learning more about the terms used to describe certain minerals has helped me in knowing what to look for & how to describe it a little better.

Colour - Black
Lustre - Vitreous
Diaphaneity- Opaque

It also has vertical striations.

Hornblende & Kyanite were suggested as possible candidates but I think the crystals are too opaque. I do not have the equipment required to do a streak or hardness test, but will look into getting some for future use

Based on those findings I think I have narrowed it down to Schorl, or Black Tourmaline, the most common form of Tourmaline.

Thanks again, I have learned quite a bit more about what to look for when identifying minerals & gems in the last few days.

Cheers, Ditch.

 

[user 4386]

Yes schorl. The striations are typical. Instead of looking at the crystals side on, I suggest you look at them end-on (in cross-section). I think you will find them to form a complex triangle or hexagon (belongs to the Trigonal crystal system).

Use a piece of broken plate as a strek plate (rough porcelain) but of course the mineral will only leave a powder if it is softer. A small pocket knife blade is around hardness 5 and you can scratch the mineral to leave powder - quartz is 7 and can be used to scratch it. But tourmaline is about 7.5 so will not scratch. The powder is easy to see if you use a hand lense (eg from Prospectors Supplies - x10 although I also use a x20)

A "gold" coin is about hardness 4, your fingernail will scratch things of 3 or less. You don't need expensive equipment.

 

[Ditch]

Yes schorl. The striations are typical. Instead of looking at the crystals side on, I suggest you look at them end-on (in cross-section). I think you will find them to form a complex triangle or hexagon (belongs to the Trigonal crystal system).

Use a piece of broken plate as a strek plate (rough porcelain) but of course the mineral will only leave a powder if it is softer. A small pocket knife blade is around hardness 5 and you can scratch the mineral to leave powder - quartz is 7 and can be used to scratch it. But tourmaline is about 7.5 so will not scratch. The powder is easy to see if you use a hand lense (eg from Prospectors Supplies - x10 although I also use a x20)

A "gold" coin is about hardness 4, your fingernail will scratch things of 3 or less. You don't need expensive equipment.

Cheers goldierocks, definitely hexagonal in cross section (did a bit more research on crystal systems). As you suggested I used a piece of quartz crystal to scratch it but it didn't leave a mark. Just for the sake of practice I tried a piece of sapphire which did leave powder behind. Also tried a piece of garnet (6-7.5) with no result.

Thanks for the tips on simple things to test hardness & I will keep an eye out for some broken porcelain plates to use as streak plates. New to gem & mineral fossicking, mainly concentrated on gold in the past, looking forward to learning more about it!

 

[David Potter]

As a geologist I would concur in saying it is tourmaline. Tourmaline can come in all sorts of colours depending on the levels of impurities. The most common is what you have found with "watermelon/spectral" tourmaline the most sort after. Tourmaline generally occurs in the later phased veining associated with felsic intrusive. activities

 

[user 4386]

One thing to be aware of is that some minerals (usually elongate or platey) can scratch more readily in one direction than another, but the difference is usually not major

 

[Lefty]

Very interesting looking specimen, whatever it is. Very difficult to tell from a photo usually, though some features can be determined that way.

 

[Ditch]

If be digging and following that peg a bit further lovely speccie rock

Had a chance to stop at the spot that I found the specimens yesterday. Took me several hours to locate what I think is the area that the pegmatite is located. Had a bit off a scratch around with the limited tools I had. Seems to be a vein around 50 - 70 mm wide at the surface. A fair bit of Mica & Feldspar around it. Did not find any other crystals apart from one small needle that seemed to have a green tinge to it.

Hopefully it might open up a bit & there is something worth the time & effort. There is around 3 meters of it exposed at the surface before it disappears under the dirt.

Was keen to go back out there over the weekend with a few more tools but the weather has closed in so it will have to wait.

 

[GypsyGoldAu]

...& I will keep an eye out for some broken porcelain plates to use as streak plates.

Forget broken plates...just visit your local floor/wall tile shop and ask for a rummage through the 'spoils' bin...
Cheers