There are plenty of glass block designs and colors in the market. We chose the "Diamond" design with no color (clear). This design seemed to shimmer in direct light. Other glass block suppliers call this design "Regent", "Checkers" and "Jewel".
After the house construction, I wrote how the glass blocks provided natural light to our living room especially near the stairs.
And the natural light was quite effective. The dark varnished steps of the stairs are brightly illuminated anytime of the day.
Shown below is a photo of the stairs, looking down, as taken from the stair landing. You'll notice how brightly the glass blocks (on the left) are from the sunlight.
Lately, I noticed some prism effects on the floor. This is when the sun directly hits the glass blocks at around 10 to 11 in the morning.
I don't know why I hadn't noticed it before, but maybe it has something to do with the current position of the sun at that exact time. The prism effect lasts only for half an hour and then fades. Nevertheless, I'm always amused when I see it.
Here's a photo of the ceramic tiles at the ground floor.
The shadows you see running diagonally from left to right, bottom to top, are those of the iron balusters of the stair railing. The squarish light-blue shape you see near the top of the picture is an image of our front windows being reflected by the ceramic floor tiles.
I wanted to take a detailed shot of the prism effect and so I shut the curtains of the front windows and closed the main door in the living room.
This is to darken the area by removing other light sources. Shutting the curtains also prevented the ceramic floor tiles from reflecting extraneous light.
This is the photo of the prism-like effect.
The above photo of the floor was taken at a different angle. Just for reference, you'll see the shadows of the iron balusters now running horizontal. You'll notice there are individual prism spots on the floor.
Below is a detailed view of one of the prism spots. That horizontal band is the floor tile grouting. I believe one glass block creates several of these spots.
Shown below are the glass blocks as seen from the floor, looking up. I had to lower the light settings of the camera to remove the glare. That's why the surrounding wall looks dark.
I think the prism effects comes only from this kind of decorative glass block. If you will look closely inside this glass block design, there are triangular patterns that disperse light the way a prism does.
There may be newer glass block designs that are better at creating these light effects. Do ask your builder or glass block suppliers for recommendations if you do plan on using decorative glass blocks for your walls.
Remember, glass blocks are not designed as substitute for load-bearing walls - just like windows. A good rule-of-thumb is this. If it's an area on the wall where you can install a window, then that's where you can install glass blocks as well.