As a young boy, had you asked for a list of tonewoods, I likely would have included Rosewood, Spruce, Cedar and, perhaps, Maple. As an early teenager, I probably would have added Mahogany. While I wouldn't have been wrong, I quickly learned that acoustic guitars can be (and have been) built from many wood species.
Several factors determine a given wood's suitability for inclusion in a given guitar build such as musicality, workability, strength, aesthetics, availability, etc. Wood species that tend to score higher with both builders and players alike are generally referred to as tonewoods.
I am of the persuasion that many of the traits and characteristics of various species of tonewoods are observable, recognizable and even distinguishable, though that does not mean that all traits are always present in every sample. I explore this topic a bit further in my article » Wood is Wood - Until it is More.
In the brief listing below I have compiled various measurements along with my own subjective and esoteric understandings of a sampling of my favorite acoustic guitar construction woods. Note that these are mostly North American species found predominantly in the Pacific Northwest region of the United States.
The information above has been collated from various online sources, including:
Janka hardness: Derived by determining the force needed to depress a steel ball a given distance into the wood. This can be useful when considered the blunting effect the wood can have on tools, as well as how easily a wood may scratch or dent.
Average Dried Weight: Expressed as an average weight of kiln-dried (not green) lumber
Specific Gravity (12% MC): This number represents the density of a wood, dried to 12% Moisture Content, and is mathematically represented as “ρ”. It is a comparative number that reflects the wood's mass per unit of volume.
Modulus of Elasticity: Young's Modulus () measures a wood's stiffness when force is applied lengthwise. It informs us of the wood's resistance to being deformed, and can aid in understanding a given wood's ability to spring back to its original position or shape. It is typically expressed in GPa (GigaPascals).
Stiffness-to-weight Ratio: Also known as Specific Modulus, this useful comparative number is arrived at using the formula / ρ. Example (Sitka Spruce): A Modulus of Elasticity of 11.03 GPa divided by a Specific Gravity (at 12% MC) of 0.42 equals a Stiffness-to-weight Ratio of 26.26.