Here is an interesting article I ran across while doing some web research:
THE INFLUENCE OF AMATEUR RADIO ON THE DEVELOPMENT OF THE COMMERCIAL MARKET FOR QUARTZ PIEZOELECTRIC RESONATORS IN THE UNITED STATES
By Patrick R. J. Brown, N7KRG
Abstract
In the mid and late 1920s, amateur radio operators were experimenting in great numbers with crystal control of radio transmitters. At the time, most amateurs used home built transmitters made from a combination of purchased and home made parts. The use of quartz crystals by amateurs predated the first U.S. commercial broadcast station to use crystal control. Amateur radio operators were the first sizable commercial market for crystals. Many of the crystal companies of the 1920s and 1930s were founded by amateur radio operators to supply other amateurs.