Generally, the sand used to make glass results in an aqua color. When manganese was added to the batch, it resulted in clear glass. Therefore, clear glass is more expensive to make and utilitarian objects such as fruit jars weren't worth the extra effort. There are however, some jars that were made in clear glass, whether they were sold at a premium because of it, or whether the blowers made a few fruit jars after completing whatever items they were making for the day - I have no idea. Of course, the items that were originally clear eventually turned amethyst with time and exposure to sunlight.I have a ground lip amethyst hero pre-1900s jar with some light amber swirling by neck.ive seen 100s of them glass hunting.every one aqua.so mine was once clear...never seen a pre 1900 clear jar..I clear pre 1900 jar would be rare right?????why where most pre-1900s one aqua???