Wondering if someone could confrirm an ID

I know this may be obvious to some but for me every polymorph ID is a first.

Am i correct in identifying this as a tridymite mineral sample

I don’t know much about minerals, being a gemologist, but from the Wikipedia article on tridymite:
<<Where is tridymite found?

Tridymite is a high-temperature polymorph of silica and usually occurs as minute tabular white or colorless pseudo-hexagonal crystals, or scales, in cavities in felsic volcanic rocks. Its chemical formula is SiO2. Tridymite was first described in 1868 and the type location is in Hidalgo, Mexico.>> {Emphasis added}

Based on the “minute tabular” part of the description, I guess you need a closer look…perhaps a macro photo? -royjohn


Thank you i will see what I can do for better pictures. Im in south central Pennsylvania and an area that is all eras mashed and mixed together. Primarily i get basalt limestone silicates quartz calcite exc. I also was on the edge of the great magnesium patch so we get dolomite as well as high iron content, pyrite, copper, gold, limonite malachite, azurite, hematite, bixbite, magnitite, garnet, mica muscovite and schist.

tridymite is a high temperature phase of quartz. If you google a phase diagram for quartz you will find alpha, beta phases with the ; alpha and beta phase being “normal” quartz… tridymite and cristobalite are high temperature polymorphs and are usually found with gas cavities of rhyolite flows. They form druze, or minute crystals and not solid pieces or chunks… the gold looking stuff is not likely to be a high temperature form of quartz, as tridymite and cristobalite are clear. The crystal structure of tridymite is triclinic to monoclinic depending on it cooling history. cristobalite is orthorhombic…and has the largest field of high temperature and pressure of the high temperature quartz phases… very high pressures form the coesite structure which is monoclinic… these higher temperature and pressure phases are denser than low temperature and pressure normal quart… From the picture it’s not possible for anymore to do more that guess what it is. Your best bet for identification is to take it to your local geology department at a local university and ask a geologist what it is… if you don’t have access, a local extension agent geologist might be able to tell you. The locale that the rock came from is very important in any ID… as it puts it into geological context.


didn’t mean to get so involved with quartz phases…but a better close up picture could help some what…
where you are the geology is complex… there were two continental collisions and a spreading into an ocean when the second collision formed the appalachians… metamorphic crystalline rocks with igneous intrusions make that area extremely complicated when it come to the geology. Mineralized zones are ancient zones and not of recent igneous activity, By recent I mean the opening of the atlantic ocean 150 million years ago.


No i absolutely love this i have autism and this stuff is my special interest!!

I got started with gems because of my stepfathers passing but as a lover of science and nature it led me to geology. As a spacial thinker i have like a jarvis in my head. I can play thoughts like movies. I started to learn about the stones my father left me and it completely changed my perspective. Like a web drawn on paper became a 3d structure. I researched the minerals. How they form it was the dolomite that made me go WAIT A MOMENT…
It was like i could imagine time pass in fast forward of what my yard looked like back to Pangia. Sometimes my weird brain is fun.

Where i live as well as where i grew up were geologically magical.

Northeast of Seattle at the base of the cascade mountains,

10 years in the bay area California near mount Diablo

1 year in Philly

York Pennsylvania a blend of WTAF ITS HOW OLD!!! West York to be exact
My area is still a big ???.
We are the map code of “well scanner wouldn’t penitrate so we took info about Apalachicola and ohio and copy pasted a best guess.”

And i am FAR from an expert but i think that theres a slight chance they overlooked a detail or 2 changing the things in the ground and how they formed

This also may have been shipped in i am in a “city”

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I am a geologist and specifically an igneous petrologist by hobby… I do not hold a formal degree in geochemistry but have learned much from reading 300 and 400 level college geology textbooks on the subject and more from research papers thru my membership the the american geophysical union. I do know enough about isotope systematics and trace element signatures to understand most of what is presented at the annual Goldschmidt conferences of geochemistry… alkalic igneous rocks is my area of first interest. Formation of ores and mineral paragenesis is part of my knowledge base… Now that I have finally retired, I am thinking of getting a degree in geology just for the fun of it.


Will you be my new best friend!!! I keep trying to tell people that i live on a line that looks like a place it pulled apart it was bracish peet bog on magnesium and then snap quick little lava injection everone tells me im wrong and the area was carved by erosion and that doesn’t seem like it is correct like ypu said im in a “complex” area and if im honest it seems like someone guessed long ago and no one bothered to question it… sorry for not getting back to you sooner but I have adhd AND narcolepsy so between time blinness and no object perminance and randomly napping i loose track of …ooh shiny.

Ill send what i can for pictures today

where you are living now, Cascadia, is a great place geologically… the area is still very active…on going subduction at the coast with the coastal ranges, and the basin which is puget sound and the Willamette valley… then the high cascades. the back side of the cascades goes into back arc spreading with basin and range…dand the columbia river flood basalts… study what you can… it’s all on line… congrants for living in a great area.

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Currently I am in west york Pennsylvania ill get you the geological pages …roadside geology Pennsylvania pg.292


  • the note below said there was difficulty getting readings and the findings are based on comparable areas of ohio and Apalachicola

now that you have the rock type locale, you should be able to identify it yourself… pictures are very hard to interpret… what looks whitish and crystalline could be quartz but it could be a metamorphosed dolomite also…the gold specks could be mica flakes in a quartzite but it could be pyrite or even gold… gold would not be found in dolomites… a local expert or local community college earth science professor could help you more than I.

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Thats how i got to tridymite and was asking for a confirmation

And you would think a local expert would know but they said thats impossible i grew up near there and then stood me up on the day we set aside for hom to come examine the collection misidentifying at least 1 item. And yes we have gold flakes muscovite and pyrite

it won’t be tridymite. tridymite occurs as a low pressure high temperature polymorph or quartz.

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But why wouldn’t it be here we have tons of quartz and it likely is local but from a building materials supplier.

my response is on the thread that you created with your first rock with a crack full of small crystals.

That wasnt me.

Thats the problem i was responding to Jennifer until you askes me questions there i am a different person but i get it all women into gems look alike lol jk

I think you missed my note here that the results are an estimation because surveying equipment wasn’t working on the land here

I also have a strong suspicion that what i think is sphalerite could be diopside. like i said still learning i assumed sphalerite because so much
was cubic but not all.

Things weren’t adding up so i plan to take it to a musium since the local college is not helpful. Like i said they estimated the land here baised on other places because they couldn’t get the equipment to work. they looked at the surface and said its probably like that other place and no one else has questioned it.

But i keep pulling things out of the soil that “shouldn’t be here” and no one has any answers. They just stop at “that shouldn’t be there your obviously an idiot.” Im new but im not stupid.