Needles are a type of selenite (gypsum) spar crystal that grows in gypsum-rich cave sediments. Like a gypsum flower, growth is from the base rather than the tip. Shorter needles are typically straight with no branching and maintain a fairly uniform cross-section as opposed to flowers. They range from a few mm to over a cm in thickness with lengths that can exceed half a meter. Longer needles may develop curves. Thicker needles are more likely to exhibit some twinning on the ends.
|Created: Nov. 21, 2016|
Author: Dave Bunnell