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What Rock is that?

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Looking at the general shape and conchoidal fractures, most likely quartz. Brazil is the quartz capital of the world I would say, especially Minas Gerais.

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There some method to calculate this specific gravity and hardness? Its the weight? 40g - 200 cts | Or i have to go to a specialist to make tests?

I risk this rock with steel blade and dont mark, but with the diamond cutter (glass cutter pen) its mark.

I risk glass with the rock.

up to 7 in the hardness scale

And its a little diferent from this glassy quartz, my rock is more clear, you can see through, ill try to take more photos! and put here! Thxn people for help me!! We´ll Keep trying! Im searching a good and not very expensive $$ lab to make tests with the rock,

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You must weigh your rock (the G value), then weigh the rock in a glass of water (after you've done Tarra) and then you know the value of Ga. So, you find specific gravity SG. Like in example:


So SG = 5g/cm3

Best regards


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Dont react with vinegar. but seems its more clean now... i can see some inclusions that i cannot see before..

Its most hard then steel blade.

Specific gravity = 2.6g/cm3

Hardness = 7 +- or more.

Strake = incolor

not fluorescent.

Rock Crystal / Qartz crystal / ....

i dunno...i ll try fisio-quimio analisis.

=)) thx for help!!

Ill post later my collection of rock, from a lot of countries.

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Hey Tom ,

I found this more than a mile from the nearest road ... all covered in dirt so in my pack it went. Everybody here knows what it is.... at least anybody over 40 that is. It is a piece of very thick tempered glass from an old insulator. But you are right Tom it did look just like yours. and my chunk weighs 46 grams

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Tom ,

I sure hope yours is indeed something very special. I thought it was strange how similar my chunk was... they sure did look alike. Mine is cold because tempered glass is not a good object to absorb heat from light instead it allows it to pass through .

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humm!! even if this is a piece of temperate glass, its already very especial!! =)) And beutifull piece! Shape of a "marine horse"

Now i beat it with another rock, and brokes perfectly! its clean clivage.

Mine have some inclusions, red and black....

Ill post the photos today night.

The rock allows good passage of light but have high refraction and bright shine reflection.rainbow inside!! =))

Thx Oredigger!!! I hope this is some rare rock!! =)))

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