CSS Background-Blend-Mode over two Elements - css

Question

Lets assume I have a div with a Gradient applied as a background-property.
I now want to overlay a black PNG (of smaller size) and set the PNG to have a background-blend-mode of overlay. Unfortunately I have no idea on how to achieve this.
I know I can have a working background-blend-mode when I render the Gradient into the CSS of the Div with the PNG image like:
background: url(../img/plus.png), linear-gradient(to bottom, #24cae4 0%, #1f81e3 100%);
background-blend-mode: overlay;
This however results in the Gradient being as small as the actual PNG, which is not a desired effect, like this:
What I want to achieve is this with pure CSS (if possible):
Here a Codepen to illustrate what I'm trying to do: http://codepen.io/anon/pen/zxOXGP
Notice the Black Icon. I wanna overlay this.

Answer 1

Try using mix-blend-mode instead of background-blend-mode and switch to simple text for the plus-sign or a webfont for more custom figures.
Example Codepen of the below:
.placeholder {
position: relative;
width: 400px;
height: 300px;
background-image: -moz-linear-gradient(#ff0000, #0000ff);
background-image: -webkit-linear-gradient(#ff0000, #0000ff);
background-image: linear-gradient(#ff0000, #0000ff);
}
.center {
position: absolute;
top: 25%;
width: 100%;
font-size: 120px;
}
.center span {
display: block;
text-align: center;
color: red;
mix-blend-mode: screen;
}
<div class="placeholder">
<div class="center"><span>+</span>
</div>
</div>

Answer 2

The gradient sandwich
Ingredients
The :before forms the bottom z-layer with z-index: 1, it is full opacity
The .content div forms the filling, central z-layer, with z-index: 2. It needs position: relative to take its z-index.
The :after forms the top z-layer with z-index: 3 and completes our lunch item. It is half opacity.
This is the tasty result:
Full Example
I have removed all but the standard CSS3 gradient for simplicity. View in a supporting browser.
.gradient {
position: relative;
height: 200px;
padding: 20px;
}
.gradient:before,
.gradient:after {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
content: '';
display: block;
background-size: 100%;
background-image: linear-gradient(to bottom, #24cae4 0%, #1f81e3 100%);
opacity: 0.5;
}
.gradient:before {
opacity: 1;
z-index: 1;
}
.gradient:after {
z-index: 3;
}
.overlayed_image {
position: relative;
width: 64px;
height: 64px;
display: block;
margin: auto;
background-size: contain;
background-repeat: no-repeat;
background-position: 50% 50%;
background-image: url(http://cdn.flaticon.com/png/256/9029.png);
}
.content {
position: relative;
z-index: 2;
}
<div class="gradient">
<div class="content">
You can see me!
<div class="overlayed_image"></div>
</div>
</div>