Fire Opal from North Uruguay?

Corning, CA(Zone 8a)

This is the stone/ rock that got me interested in rocks a few years ago. i found it along with many others along a river outlet on the beach in uruguay. I followed the river up to the north and the stone originates there ... In Uruguay where the famous amethist is mined of the highest quality. There are many thermal springs in the area. I am wondering if this piece might be a polished piece of citrine or other golden type of crystal that is found in the area....or could it be a fire type opal that you find in Mexico. I found lots of them. IS there a test that can be done to see if its opal or just crystal like citrine? or topaz? when i first looked them up I though maybe amber pieces then i thought tecktites since many had glass like appearance and the thumb print like texture as if it was golden glass colors range from dark blood red to golden yellow and oranges.... ideas?

Here are some other examples that look just like the samples that i found.$%28KGrHqF,!h8E2I+UCyWsBNm4965-vQ~~_35.JPG$%28KGrHqZ,!iIE2Ks46oQoBNn1imq49g~~_35.JPG
thin like this and same color and everything.. cold quartz be polished on beach and river like this? or?

Thumbnail by leeannconner
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