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[AlbionFireandIce]

Hi guys,

This is a Botswana Agate tumblestone I bought in a 1KG bag from a wholesaler; it doesn't look especially like classic Botswana Agate to me but thats a whole different story.

It has an inclusion of coral or something similar in. Looks like it might be Hexagonaria or similar - are there any coral experts on here who could help me narrow it down? I've never seen anything like this before and I'm very taken with it.

Thank you,

John

[yukonjade]

  The stone looks a lot like mud river agate from Madagascar.

[AlbionFireandIce]

  The stone looks a lot like mud river agate from Madagascar.

Could well be, none of the bag looked like Botswana Agate to me. Wasn't too bothered after I found this one, though.

[lapidaryrough]

with a Horn coral plug. 

 basalt flow below water level ( Salt water ) well have calcite Crystal formations, forming in the gas pockets. then the basalt flow rises above sea level to form the agate beds in around Lebanon Oregon. an Sodaville Oregon Lebanon is my home  town, first rock pile.

   The gas pockets in the basalt have  calcite formations In the pillow  basalt  70% silica. in ( Oregon )
every river you'll  find agates / jasper / iron.
  The calcite roots away leaving the foot prints of the calcite growing in the agate cavity, on the face of the geodes ( Hollow or solid )  as dug in Lebanon on Rock hill Rd.   yellow - dark red ----  Down the road three miles  The Blues purples pink agate. around the corner too the wood pile. and up the road too Quartzville cr. for camp.  ( Love my BACKYARD )

 Jack lost in Mine & Rock

[AlbionFireandIce]

A few more photos, hopefully showing the depth of... whatever this is!

[lapidaryrough]

Horn Coral tip,  encapsulated with a sedimentation of silica. 

[AlbionFireandIce]

Horn Coral tip,  encapsulated with a sedimentation of silica.

That looks spot on, thank you.   

[irockhound]

Looks like sagenite to me, especially with the 2nd ring with obvious needles.  Often Sagenite forms in balls, I have Nipomo Sagenite that looks like 2 half balls side by side and have found the same dome structure in Sagenite in Horse Canyon and other locations.

[lapidaryrough]

https://www.google.com/search?q=fossil+horn+coral+photo&client=firefox-b-1&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiW9e7OhtrXAhVFON8KHWznAxMQsAQINw&biw=1268&bih=884

   toprock.com So Africa Keith May, mines Madagascar for their stock for web-site.

  https://www.toprocks.com/

   Keith May Knows erevy corner of the rock pile known as Madagascar.

   John Borun does the finger stones. on the toprock site.

  you'll see in link / fossil on page. an rough section ''   Botswana Agate   ''

  Star rose quartz  6 ray.

[gemfeller]

I tend to agree that it's a sagenite ball.  I've seen them frequently in various agates.  Here's one in a Laguna agate cab I cut from the heel end of a nodule. 


DCab 3B.jpg (85.04 kB . 372x450 - viewed 251 times)

[irockhound]

I have never heard of Coral associated with Botswana however if you search for sagenite and botswana you will find tons of examples.  I am not saying it can't exist but if it does it must be exceedingly rare.  Also if you open the first image in the pics posted you can see from the patterns of the hair like sagenite radiating out it is obvious that it is not a coral.  I have been unable to even find an image in searching of a coral in Botswana agates. 

[AlbionFireandIce]

I have never heard of Coral associated with Botswana however if you search for sagenite and botswana you will find tons of examples.  Also if you open the first image in the pics posted you can see from the patterns of the hair like sagenite radiating out it is obvious that it is not a coral.  I have been unable to even find an image in searching of a coral in Botswana agates.  Just because it is circular doesn't make it Coral.

You may well be onto something there; I was put off Sagenite as most of the pieces look nothing like this one. I did find this which is quite similar, though.

https://i.pinimg.com/originals/86/a8/66/86a86653b8a4a99cf783e6bf0cc25870.jpg

It's strange that there is depth to my piece and not to this one, though.

[rocks2dust]

It's strange that there is depth to my piece and not to this one, though.

"Sagenite" is a catch-all term that refers to various minerals that can form sprays and orbs of needle-like crystals. Depending on the mineral and the environment, those minerals can later be dissolved and either leaves a hollow, or can be replaced with yet more agate or other mineralization. When replaced by other minerals, what you'd have is a pseudomorph of the original crystals. Assuming that your piece is typical vesicular agate from Botswana or Madagascar (formed within basalt flows), then your piece would have resulted from a zeolite or similar orb-forming mineral growth along the wall of a gas pocket inside the basalt. This would have been encapsulated in agate, before an alteration (such as acidic water or gas) dissolved the orb and needles. More silica would have eventually filled up the void left by the dissolved mineral.