What happens when nearly one billion Joules of lighting energy strikes sand? These tubular formations are typical of the result! With temperatures reaching 30,000 degrees Kelvin, the sand is melted or vaporized, leaving behind these amorphous glass tubes. Each approximately 2" long sample comes in an easy-to-open plastic case. A great addition to your Weather or Geology unit! These are natural products and in relatively limited supply, specimens will vary in size, shape, and color.