Micartas aren't' "just" plastics.
Micarta is layers of wood, canvas, linen, or paper bonded together.
To produce it, sheets of material are impregnated first with colored dyes, then with a phenolic resin.
The sheets are then stacked together to the desired thickness. The stack is put under tremendous pressure and heat, which bonds the whole thing into one solid sheet.
The advantages of Micarta are, it's pretty well impervious to weather, most oils and solvents, and is EXTREMELY durable and tough.
Since it's made up of thin layers, the more angles and cuts you make in the material, the more the "grain" shows.
In the wood micartas, this can make extremely fancy grips, in which the actual wood sheets themselves are fairly plain wood.
Canvas Micarta makes extremely durable grips, with a natural rough texture which offers a good grip, without checkering.
Linen Micarta, made from linen cloth, makes fine-grained material that can be polished to a glossy surface, or checkered.
This was the earliest of the micartas, and usually came only in dark reddish brown, which was used in electronics, for which purpose Westinghouse invented it.
Today, it comes in black, green, maroon, brown, and some multiple colors like maroon layers with other colors intermixed.
White paper Micarta is the closest synthetic to real elephant ivory.
Since ivory grows in thin layers, the thin layers of paper Micarta have a grain that looks very much like real ivory.
Micartas are sold under a variety of trade names, including Dymondwood, Pakkawood, Westinghouse, and others.