Prehnite is a translucent to transparent hydrated calcium aluminum silicate in the orthorhombic crystal class, usually found in radiating botryoidal (grape-like) aggregate forms, and rarely as tabular and pyramidal crystals. Prehnite is sometimes confused with apatite, jade or serpentine.
 
Apophyllite is a mineral occurring typically as white glassy prisms, usually as a secondary mineral in volcanic rocks. It is a hydrated silicate and fluoride of calcium and potassium.
 
Stalactites usually grow when silica rich waters drop their dissolved minerals when encountering changes in environmental and chemical conditions.
 
A stalactite is a type of formation that hangs from the ceiling of caves, hot springs, or even structures such as bridges and mines.
 
A stalagmite is a formation that occurs when stalactite drip to the ground, creating columns, rising from the floor of a cave. They often unite with the stalactite.
 
Easy to know the difference by remembering a stalactite holds 'tight' to the ceiling and a stalagmite grows 'mighty' from the ground.
​
Cave formations take millions of years to form.
 
***************************
* Photos show all sides.
* Sizes, shapes and colors my vary due to being a natural stone, being hand-carved and/or difference in computer monitors.