Hi Karlis,
I have some small ones found in Middelburg and Amsterdam in the Netherlands.
In Middelburg they were found near the remnants of a furnace at the Blindenhoek and in Amsterdam on the site of the glass house the Two Roses

This is a greenheart tube found on the site of glashouse the Two Roses among other colored tubes.

Superficially they look similar but the early ones from Holland are smaller in diameter and the red layer is thicker while the green is thinner. I have examples from both A'dam and Middelburg.

The ones I illustrate are much more recent. Too crude for Venice or France. But where then???

Hi Karlis,
From which sites did your green heart's come from?
By me two Middelburg sites are known, the Blauwendijk en Blindenhoek.
And you remember from which Amsterdam glashouse? thx