Are we ever told what duranium and tritanium are?

Question

Star Trek has been making up fictitious materials since season 1 -- dilithium, for instance, which (in an Animated Series episode, was said to have a helical structure similar to DNA).

Some of these, however, have similar names and are used in similar contexts to real world materials. For instance, Duranium, which we're told comprises the internal partitions in the Enterprise D, seems linguistically similar to "duraluminum" -- which was an aluminum alloy used for aircraft frames and skins for many years, before the name fell out of favor, replaced by more specific alloy names -- and titanium, a metal both lighter than aluminum and stronger than steel. We also hear about Tritanium, the main structural material of the Enterprise D, which also sounds like it might be a titanium alloy.

Obviously, there aren't a bunch of newly discovered elements in the 22nd, 23rd and 24th centuries, so these materials have to be compounds or alloys, or they'd be too radioactive to use in ships for long term human occupancy (all elements above atomic number 92 are radioactive to some level).

Are we ever actually told whether Duranium and Tritanium are actually titanium alloys or allotropes (alternate crystal habits) of titanium, or Something Else?

Answer 1

Frame Challenge

A lot of the question is based off the erroneous assumption:

Obviously, there aren't a bunch of newly discovered elements in the 22nd, 23rd and 24th centuries, so these materials have to be compounds or alloys, or they'd be too radioactive to use in ships for long term human occupancy (all elements above atomic number 92 are radioactive to some level).

Per VOY1x09 "Emanations", there are 246 known elements, with Voyager believing they've discovered a 247th.

"Captain's log, stardate 48623.5. There are two-hundred-forty-six elements known to Federation science. We believe we have just discovered the two-hundred-forty-seventh inside the ring system of a class-D planet."

Tritanium

Memory Alpha has plenty of on-screen references to the properties of tritanium. It's apparently found as an ore known to be 21.4 times as hard as diamond. Per the Star Fleet Medical Reference Manual, a reference book written from an in-universe perspective, the element tritanium uses the symbol Tn, has atomic weight 323, and atomic number 125.

It's used in starship bulkheads, armor plating, as part of an alloy for shuttle hulls, engineering tools, and even bullets for projectile weapons. It must be pretty common, or at least widespread, because Alpha Quadrant, Beta Quadrant, and Delta Quadrant powers make use of it.

Duranium

The Star Trek: Deep Space Nine Technical Manual, another reference book written from an in-universe perspective says duranium is naturally-occurring, and mined from worlds like Bajor (presumably alongside the uridium DS9 processed). The fact that it's mined suggests duranium is not an alloy, supported by the use of the term "duranium-235," which in normal chemistry nomenclature means "an isotope of the element duranium with an atomic weight of 235".

It's used in similar ways to tritanium: starship and shuttlecraft structural members. One notable stand-out use is in transporter calibration - in TNG3x31: Hollow Pursuits, O'Brien uses a "pure duranium" test cylinder as part of an inspection/repair.