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Rock Id


Jonnyp

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Hello everyone,

My niece (4 years old) has this rock as her prized posession. She has entrusted it to me with the mission of finding out what it is made of. I could really use some help from experts!

The picture that looks more pink is closer to the natural color than the yellow looking pictures. (Poor Lighting)

The darker colored sections can scratch a glass bottle. The pink can not.

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Thank you so very much for your time!

Jon

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I usually lurk nowadays instead of commenting...but I couldn't help it on this one. It looks like your niece has some schorl (black tourmaline) inside what is mostly quartz (rose quartz if the colors on my monitor can be trusted). There are surely some other minerals in there, likely feldspar and mica. This appears to be from a granitic pegmatite, a section of granite that has cooled slowly to produce much larger crystals such as the nice black tourmalines.

These are my favorite types of rock, because they often have little hidden secrets if you look close enough.

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I reckon it's quartz, with a bit of other stuff that i can't identify. 4 years old and already interested in geology. Great start!

"In Africa, one can't help becoming caught up in the spine-chilling excitement of the hunt. Perhaps, it has something to do with a memory of a time gone by, when we were the prey, and our nights were filled with darkness..."

-Eternal Enemies: Lions And Hyenas

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Yep, those black phenocrysts are tourmaline crystals. Tourmaline is pretty hard on the Mohs scale (7-7.5). I would guess the matrix is largely feldspar which is frequently pink and in the same hardness region as bottle glass. Typically 6-6.5 for feldspar versus 6-7 for bottles, depending on the quality of the glass. If it’s a lot softer, then it probably also has muscovite (mica) which has a hardness between 2-4 depending on whether it’s measured parallel to or perpendicular to the crystal planes. The crystal structure does look a bit ‘platy’, which would be typical for mica. Quartz (with a hardness around 7) would normally scratch all glasses apart from high tech material.

Tell your niece she’s found a gemstone. Treasure!

Roger

I keep six honest serving-men (they taught me all I knew);Their names are What and Why and When and How and Where and Who [Rudyard Kipling]

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… and tell her that tourmaline comes in such a wide variety of colours because – according to legend – it travelled across the rainbow. Also that we’re all very jealous of her treasure. :)

Roger

I keep six honest serving-men (they taught me all I knew);Their names are What and Why and When and How and Where and Who [Rudyard Kipling]

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Wow, thank you all very much for your expertise. I didnt realize she had such a prize!

I will be certain to pass along the mineral types, formation, and egyptian lore!

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