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[surendra]

Hi Experts,

I am from Sri Lanka. I found below specimen when I was walking on a river bank. I found very deep red stones in the matrix. The stone sizes are varied up to maximum 1cm. I tried to scratch on a mirror and it did. What can be these small deep red stones. Can it be pyrop garnet or some other mineral?. I have observed some mica particles also included in this specimen.

One more thing.... In another side of the specimen I found these red stones are with some blue/black coloured stone. What is this blue/black color mineral. Is it 'genesis'. Can some one tell me about the hardness of gneiss when comparing with 'Quartz'. Is it lower than 7 in Moh Scale? Please give me the answers. ( I am pretty new to geology and I am trying to get an education on this field by observing the things) Thanks in advance.

-Surendra

[nicu]

Hi,
The location would help for identification. Are required to begin the hardness testing. The reddish-brown mineral like garnet this. The specimen would seem is that garnet-sillimanite schist. Hardness testing might also indicate blue corundum mineral if this scratch the garnet.
Regards,
Nicu

[prcantos]

Hi. I agree with Nicu, it looks like a garnet schist. Red spots are garnets (it's difficult to say the exact name without technical analysis, and even so may be impossible to decide because of isomorphism). Blue material might be kyanite if you have high pressure metamorphic rocks in Sri Lanka (I don't know it, but may be possible according to global tectonics). If this hypothesis is right, garnets might be pyrope, the most usual garnet in these high pressure facies.

[surendra]

Thanks Pablo and Nicu for your valuble comments. I have palnned to find out the refractive index for the deep red color stones.

For blue color stones, It is NOT transparent and can easily be brocken in to pices.

Actually I removed this speciment from a very large rock (1m*10m*2m). And I have observed this red color stones were in whole area of the rock. Do you feel this rock can be a rich source for precious minerals other than garnets. Can there be corundums (Rubies). As I have observed some parts of the rock are very rich with mica.

Appreciate if some one can explain the possibilities of the other minerals can be exsisted in this rock.

Thanks again for your valuble comments given to me.

Regards,
Surendra

[prcantos]

Mica is also an essential mineral in schists. Corundum may appear in these rocks as an incidental mineral, you can recognize it testing its high level hardness (9 Mohs). Schists usually bear many different minerals depending on the zone: staurolite, kyanite, andalucite, garnets, cordierite, turmaline, zircon, pyrite, magnetite, chloritoid... Anyway, I am not interested in precious minerals or gems, I cannot give more information about that.

[surendra]

Thanks Pablo for the given information. I really appreciate your information and the given guidance.

Thanks again.
Regards,
Surendra

[Riccardo Modanesi]

Hi to everybody!
Blue mineral: if so easily broken, it might be kyanite in my opinion too.
Red mineral: it could be easily detected whether a garnet (pyralspite, maybe almandine or pyrope, probably the former one), or a corundum (in this case a ruby). Put the specimen under a UV light. If not fluorescent, it is a garnet. If fluorescent (evident brilliant red colour), it is a ruby.
I hope I was useful for you.
Greetings from Italy by Riccardo.

[surendra]

Thanks Riccardo.... Those information was very valuable for me. I have planned to get the values for Specific Gravity/ Refractive Index/ Hardness test. I think testing against the black light will definitely helpful to identify the specimen. Thanks a lot Riccardo.....

Regards,
Surendra

[Pete Modreski]

Surendra,

If the blue mineral is not very hard (you can scratch it with a knife point; hardness =5) it could likely also be apatite; blue apatite is common in pegmatites (along with quartz, feldspar, mica, garnet, beryl, etc.) and it is, I must add, not of any particular value, unless it is very nicely crystallized.