yes
Tetrahedrons and quadrilaterals.
good question
tetra means four.
Double tetrahedrons come in different sizes and complexities. The current online resources have no user diagrams, but some books may. You may want to consult the related link for suggestions.
yes
Tetrahedrons and quadrilaterals.
Tetrahedrons are 4-sided solids. A regular tetrahedron is the equilateral pyramid, having one pyramid as the base and three others the sides.
tetrahedrons
polymorphs
good question
tetra means four.
Two regular tetrahedrons connected face to face make a "regular triangular dipyramid." That is one of the 92 "Johnson solids." Those are the convex polyhedrons whose faces are regular polygons but do not belong to either of the two sets of highly symmetric polyhedrons (the Platonic and the Archimedean) or to the perhaps less interesting two infinite families of prisms and antiprisms. If the two tetrahedrons overlap, both centers at the same place but with the tetrahedrons facing in opposite directions, it makes a "stellated octahedron."
Silicate minerals.
More like two tetrahedrons stuck together.
Double tetrahedrons come in different sizes and complexities. The current online resources have no user diagrams, but some books may. You may want to consult the related link for suggestions.
go to your local game shop and ask for a d8