•  Silk is obtained from the cocoons of silk worms. Sericulture(the cultivation of silkworm) was developed in China 2600 B.C. Silkworms feed on mulberry tree leaves. Exporting of silk worms eggs or mulberry tree seeds was made a crime punishable by death in China at that time. For about 3000 years silk making was only done in China.
	• Asphalt is both naturally occuring as in the La Brea tar pits and is also a by product of refinining crude oil. The lighter hydrocarbon molecules are removed to obtain gas and oil. The heavier hydrocarbon molecule residue leaves asphalt. This is why asphalt plants are often next to refineries. Asphalt is also the name for the mixture of asphalt and gravel that is used as a building material for roads.
	• Amber, rosin and gum arabic are obtained from tree sap. Gum arabic is the sap from acacia trees. It is used in making mucilage glue and is also used as a thickener in food products such as candies. Rosin is also from tree sap and used to increase friction. For example it used on the bow of violins and by baseball pitchers. Amber is is fossilized resin.
	• Natural rubber is also obtained from tree sap from certain tropical plants. The rubber is now used today to refer to both natural and synthetic rubber.
	• The word rubber was used because it was found that rubbing it on pencil marks was able to remove.

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