The natural materials used to make the frames are shells, ceramics, special wood,bamboo and animal heads/bones. Generally, wooden frames and horn brackets are rare, which cannot be massively produced.
It is a spectacle frame made of clam shells sourced from the tropical sea. It is mainly produced in the West Indies. The advantages are light weight, beautiful luster, easy processing and polishing, plasticity when heated, bonding when heated and pressurized, no irritation to the skin, and durability and preservation value. It is a high-end product in all kinds of glasses frames, and is very popular among male wearers of middle age and above. The disadvantage is that it is easy to break compared with materials such as celluloid, but it can be bonded and repaired after breaking. In the display of the counter, water should be placed to prevent drying. When using the maintenance, it should not be ultrasonically cleaned, otherwise it will be white and tarnished. Because cockroaches are animals that are forbidden to be captured in the ocean, so the cost is expensive. Nowadays,there are still some brands would apply shells as components into clothing(shell button,decorations),eyeglasses decoration.
Frames made of horns are not common to public until the beginning of the 21st century.Another factor is the complexity and difficulty to manufacture horn eyeglasses,due to the different horn sources with different natures, temperature influence and shrinkage ect..Horn is a kind of material hard but brittle.
Folding mixed material
The frame is made of a mixture of metal and plastic,or titanium with plastic,metal with wood or any other multiple materials combined. Some of those frames are made of metal, that is, partially or completely wrapped with cellulose acetate or windsor( a kind of slim rim of acetate produced in Italy or Taiwan); others are made of different materials in different parts of the frame, that is, the front frame is plastic/acetate, the temples are metal, or the front frame is metal. The temples are made of plastic/acetate; some use the above two methods, such as plastic for the eyebrows and nose bridge, stainless steel for the frame, and metal for the temples.
The hybrid frame is exquisite and beautiful, giving a sense of elegance. Because the outer plastic is in close contact with the inner metal material, it is not easy to burn, which increases the strength of the frame.Besides,the combination of double or multiple materials will increase the lays of graphic,contrast,sense of design and also enrich the colors of the sunglasses/eyeglasses.