First of all, look at yixing teapot’s color. For a new yixing teapot, although real zisha clay (purple clay) teapots have many colors, it is not bright, but a dim light. If the color is too bright and glare, it is likely not made by authentic yixing raw ore. For some zisha teapot which already used a while, there should be mild light, but the same will not be dazzling color. If your zisha teapot used a long time but the color won’t change, then it most likely a fake clay yixing teapot.
Above is the fake yixing teapot
Second, smell the odor. New zisha teapot generally smells only dust and HuoQi(火气), in short it’s the smell of natural clay burnt by fire, no other smell. If you buy a new yixing teapot smell like the chemical, or other pungent odor, it is likely a fake clay yixing teapot. The authentic yixing teapot after used a while, will emit a faint tea aroma. Bellow are the yi xing teapots just from kiln, sillica sand on it.
Third, listen to the yixing teapot’s sound. With the lid on the spout gently across, if it is an authentic yixing teapot, sonorous voice should be such as jade-like, crisp, and have a clear sense of sandy friction.
Fourth, touch the surface of yixing teapot. The surface of a new yixing teapot is not smooth, hand feels there should be sand grain texture. If the surface feels very slippery, it would be polished with wax, or not the authentic zisha clay.
Fifth, see water in the surface of yi xing teapot. The authentic yixing clay teapot, cause of zisha clay characteristics and pore characteristics of finished yixing teapots, to the surface in an open water washout, should be able to form a water film, commonly known as "hanging the water(挂水)", the surface of the water film should be very uniform, and can quickly dry. When you’re using open water washout, the surface was like drops of water spread out, rather than hang evenly on the surface of the water film, it is likely not authentic clay or surface after handling chemical.
Sixth, put yixing teapot in boiling water. The authentic yixing clay teapot has natural color, do not add any chemical dyes. If put it into boiling water, the color of teapot surface fades, the water color varies widely, then the pot is a fake, at least add other chemicals.
The points above, also applies to the identification of all yixing clay pots. Based on the points above, can’t 100% identify that a pot of clay used in fake, but if meet more than two of points above, then you’d better not to use it.