The term Olive Ash does not refer to any specific species of Ash, but instead is in reference to the darker, streaked heartwood found in some Ash trees, which tends to resemble the wood of Olive trees in the Olea genus.
And it should come as little surprise that Olive Ash can be a dead ringer for actual Olive (with the exception of the porous grain structure, which gives its true identity away easily), because both Ash and Olive are placed in the same family: Oleaceae. It has been finished with multiple coats of an eco-friendly waterborne lacquer which requires no maintenance other than dusting.
The Bog Oak lid has a handcut 12tpi thread and corresponding insert ensuring a secure closure. Bog Oak, much like Brown Oak, is not a specific species, but is rather a term that designates oak that has been buried in a peat bog for hundreds or sometimes thousands of years. The extremely low oxygen conditions of the bog protect the wood from normal decay, while the underlying peat provides acidic conditions where iron salts and other minerals react with the tannins in the wood, gradually giving it a distinct dark brown to almost black color.
Though Bog Oak does not describe a specific tree, it tends to most frequently occur in the United Kingdom, with English Oak being the most commonly salvaged species taken from bogs. Since there is such a limited supply of the wood—with Bog Oak essentially being the very early stages of fossilization—prices for this type of wood are very high.