I adore what I like to call "bonus crystals," which are crystals that have more than one crystal or mineral structure in them. I have several in my collection including some cool pseudomorphs, which are crystals that contain a single mineral but have the form of another mineral they replace. The two below are great examples of bonus crystals containing more than one mineral.
On the top left is a combination of sunstone (orange) and iolite (grey/blue) in a quartz matrix. Iolite is also known as water sapphire and is a great visionary stone as well as one that enhances self expression, while sunstone is a feldspar crystal that supports positivity and creativity. The combination makes this a wonderful crystal for bring unusual creative ideas to fruition, and it's also a highly empowering stone. The clear quartz magnifies these qualities.
On the top right is a smoky quartz cluster with red hematite phantoms. Phantoms in crystals are pre-existing crystals that a new crystal grows around. So in this case, it was once a red hematite crystal, but smoky quartz grew around it. Red hematite is a very grounding stone, as is smoky quartz, and when I hold this I can immediately notice myself grounding deeply into the planet.
On the bottom left is one of Jim's crystals. It's a zeolite (which is a group of alluminosilicate crystals) that has pink apophyllite completely covering mordenite, although you can see on the ends the mordenite. Mordenite is an excellent crystal for removing distractions, improving focus, and helping one see emotional situations from a more detached perspective, while pink apophyllite helps heal and release old emotional wounds. Therefore, this is an excellent crystal for releasing and healing emotional baggage that no longer suits you.
On the bottom right is a large geode with what I suspect is citrine druze with a large honey calcite piece in it. Citrine is a stone of prosperity. It also encourages self-expression. Honey calcite supports persistence and strength along with self-esteem. Both are also third chakra crystals that strengthen personal identity and self-image.