As an expert on the subject (I am not an expert on many things, but for this one I am, unfortunately), let me warn you of certain things.
First, in order to OD on heroin, your tolerance should be close to non-existent, especially for such a small dosage.
A gram is not little, but for your particular goal it very well might be.
The photo you posted shows the so called "cheese", which is heroin mixed with various additives to enlarge the weight of the "product".
The color of pure heroin is brown, the darker the better, and it usually comes in small chunks (like little rocks), which are then crushed if snorted or placed in a table spoon with water and a lemon concentrate (limuntus, sodium citrate) - if to be injected IV.
You need very little sodium citrate, but it's essential for the H to be dissolved in water.
Most of the cases of heroin OD's are intravenous injections.
Rarely do people die after just snorting the stuff (unless it's "mountains" of it).
If you have taken heroin or any other opiates recently (like the ones prescribed as pills), your brain and opiate receptors may have developed certain tolerance, so this 1g dosage will not be nearly enough to off yourself. You may end up in the hospital, or just feel great for a day, or vomit and feel miserable (which is often the feeling of the "first timers").
My point is - either increase the dose if you insist on snorting (and increase it significantly, perhaps 3-fold), or get an insulin syringe (small one) and apply it intravenously. Both options would significantly improve your odds/chances, but would still not be a guaranteed success.
PS. If the H is just a way for you to get relaxed and then hang yourself or use some other more reliable method, then 1g is OK and ignore my previous comments.
But if the "smack" is your primary hope, then please reconsider.
The best of luck in achieving what you desire and find peace.
