Is this glass or a mineral? Weirdest beach glass I've seen!

by B.M. Fiorito
(Williamsburg, VA)

pyrite layer?

pyrite layer?

~ sea glass question submitted by B.M. Fiorito, Williamsburg, VA

ID on Sea Glass found at Rappahannock River in Virginia.

By no means am I a sea glass expert or even an amateur. But I have seen sea glass, which is why I begin here.

This item was found on a small shore on the Rappahannock River in Virginia.  Size: 1 7/8" at longest side, 1/2" thickness

Reasons it may be sea glass:
  • It is somewhat translucent, though more so on the edges.  
  • It is a striking blue color, as glass can be, and I have no idea what rock/stone
  • can have such a vibrant natural color here.
  • It has a very interesting triangle shape that does not look natural to me, as it
  • has an even ½” thickness on the edges.

Reasons it may NOT be sea glass:
  • The tips of the triangle shape are more yellow/brown-blue than blue, while the middle is a very dark blue (pics are true to color). The item loses its translucency towards the middle, and becomes very opaque.
  • The soft parts have small but smooth bumps like stippling. NOT as smooth as frosted sea glass. Nor does it seem to really have a frosted look about it.
  • It has some type of sediment/orange rock layer that is very hard and will not chip off. Between the blue item and this orange layer seems to be pyrite. I have never seen glass with rock/sediment
    adhered to it…
  • There are spots that seem almost like streaks breaking through into the opaque middle part, which I don’t think occurs in glass…
It definitely is translucent when I hold it up to the light, but what is interesting is that the edges are light, almost a light brown to clear, and the blue gets a darker color towards the middle (of course it is thicker in the middle as well which can lend to its darkness).

It almost looks like a clear stone injected with blue pigment since it does not spread in a perfectly gradual way. And there are portions that are very opaque  -  even light creamy blue more which is more noticeable when wet, as one of the pictures shows.

Here are two pics of the myster mineral or glass when wet.

Mystery sea glass or mineral rock

The darker orange brown you see is NOT part of the item, just sediment or rock that has adhered to it. When wet, this item shows more lighter blue opaque areas, which also makes me think it is NOT glass...

Mystery sea glass or mineral rock

Any clue what this may be?

My husband thought it may be quartz with cobalt pigment, but we don’t know if that happens naturally…

Any ideas would be helpful!

~ sea glass question submitted by B.M. Fiorito, Williamsburg, VA

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Comments for Is this glass or a mineral? Weirdest beach glass I've seen!

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May 22, 2018
I'd like to guess.
by: robert Garfield nj

It maybe a fragment of fresnel lens? You can try to light it up with a laser pointer to see if it is transparent. It works better than a light... Just watch your eyes. You

Sep 29, 2016
Mystery Solved?
by: BM Fiorito

After some internet research, I believe that my mystery item is the mineral Cordierite.

The description of it being opaque and transparent, changing color in the light from light opaque blue to blue and yellow brown, seems to fit it.

Pictures and information of this mineral can be seen here:
and here:

Interesting what the Rappahannock will spit up!


Hi BM, unfortunately the above link doesn't seem to be working. We looked at other photos of cordierite and we still have doubts about the identification of this interesting piece.

David and Lin davidadmin @

Sep 25, 2016
by: B.M. Fiorito

BTW - how did you make a comment and load pictures? I don't see an option at all around the "Your Comments" section....??


Hi B.M.,

We (OdysseySeaGlass) uploaded this ourselves. Contact us to add photos. If you have a photo uploaded to the internet, put the URL in the comment and we will add the photo.

David and Lin at

Sep 25, 2016
by: Karen Holland

Sigh - the only similarities seems to be that part of it looks like glass. The rest of mine looks similar to what cement would be, which doesn't make sense either, along with a little bit of crystallization.

Here it is wet.

It may be of similar origins.

Sep 25, 2016
Fused glass?
by: Karen Holland

Not sure. But I have found "glass" fused w rock like this. I need to take a photo while wet. Any similarity?

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