If the specimen is approximately an inch thick and is polished flat on both sides perpendicular to the fibers, then an unusual optical phenomenon can be seen. The fibers will behave like optical fibers and transmit an image from one side of the specimen to the other. In other words, a good specimen, resting on a newspaper will have the writing appear to be on top of the specimen without any distortion of the lettering. This is a phenomenal optical property that will stun anyone who has not seen it before. This effect is partially the result of the large spaces in the sodium octahedral chains mentioned above.
Color is white or gray to colorless.
Luster is silky. Transparency crystals are transparent to translucent. Also as vein-like masses of parallel fibrous crystals. Cleavage is perfect in one direction. Fracture is fibrous.