Why does the Orthorhombic crystal system have 3 different crystal types?

Question

Why does the Orthorhombic crystal system have 3 different crystal types?
The Orthorhombic crystals have 3 axes at unequal lengths and faces at 90 deg angles. Why does this result in 3 different crystal types [dipyamid,prism, scalenohedron]? I think there should only be a single Orthorhombic crystal type as there is only the one, same set of axes? Obviously this is incorrect and I cannot see how the 3 axes at unequal lengths set produce three different crystals- all Orthorhombic. Any help is greatly appreciated.
Thank you

Answer 1

You're right, obviously there aren't three different crystals because it isn't possible. Good question, wish I could explain it.

Answer 2

Yes Quite a question I can understand Why you think that
Are you familiar with optical Indicatrtx
http://bullard.esc.cam.ac.uk/~barnett/poems/opticindic.html
http://edafologia.ugr.es/OptMine/intro/indibiaw.htm

Here is my input
The orthorhombic crystal system has three crystal habits
these three crystal habits belong to the orthorhombic system obvious These three habits or minerals in these habits are of different chemical composition,
same composition same habit,
different composition different habit.

Just to confuse the issue
Olivine Group Peridot Forsterite Mg2(SiO4) Fayalite Fe(SiO4)
still Peridot both of them
Here are three gemstones of the orthorhombic crystal system
with three different crystal habits or forms

Prismatic, abundance of prism faces
Chrysoberyl

Tabular,Rectangular shapes
Prehnite

and Acicular long slender crystals
Variscite also called utahlite

But these can cross over

Also the chemical composition governs differences in crystal structure
this first is an index of crystals with photo's 3d crystals forms with colour faces labelled
http://webmineral.com/data/Alphabetical_Listing.shtml

http://www.mindat.org/index.php
http://dave.ucsc.edu/myrtreia/contents
you have rekindled my interest thankyou