Is this stamp a "forever" stamp?

Special $1 Rhodonite stamp from the Rare Beauties set

This special stamp was released on 31 March 2017 at the Melbourne Stamp Expo.  It was the single stamp in the Day 2 Minisheet.  It differed from the other $1 Rhodonite stamps.

1)  It had a lump of rock attached.  The rock was 2mm high and stuck near the top right corner of the stamp.
2)  It was a different size = 27 x 36.5mm.  (The other $1 Rhodonite stamps were 26 x 37.5mm.)
3)  It had a different perforation = 14.1 x 14.3.  (The other $1 Rhodonite stamps were 14.6 x 13.9.)

I wondered how the rock would survive going through the mail stream.  I put a piece of cardboard in an envelope, sealed the envelope and affixed the special stamp.  I addressed the envelope to myself.  I have posted it in roadside mailboxes around Melbourne.  Here is it's postal history to date:

Postings #1 - #2:  No change.  Rock intact.  No postmark.

Posting #3:  Rock removed.  Black barcode on front.  Red barcode on back.  No postmark.

Postings #4 - #11:  No change.  Still no postmark!

Posting #12:  Red barcode on front.  Black "DLC 992-4, 19:27, 17/10/2017" codes on front.  No postmark yet!

Posting #13 - #14:  No change.  Still no postmark!

Posting #15:  Watch this space !!

Updated  14 August 2017

$1 Rhodonite Stamp Summary

This stamp was issued/released as follows:  [Sheet stamp + 10 variations]

Perforated gummed stamp (Issued 30 March 2017) - Sheet (se-tenant with $1 Golden Sapphire stamp), Prestige Booklet (Block of 4 of the same stamp, Se-tenant block of 4 with other $1 & 2 x $2 stamps), Minisheet (se-tenant with other $1 & 2 x $2 stamps).

Imperforate gummed stamp (Issued 30 March 2017) - Imperforate Prestige Booklet (Block of 4 of the same stamp, Se-tenant block of 4 with other $1 & 2 x $2 stamps).  [Individual stamps not valid for postage.  Only whole pages are vaild for postage.]

Self-adhesive stamp (Issued 30 March 2017) - Booklet (with $1 Golden Sapphire self-adhesive stamp).

Cancelled gummed stamp  (Released 31 March 2017) - Special Expo Day 2 Minisheet attached to a Medallion Cover (pair of stamps).  [Stamps already cancelled hence not valid for postage.]

Special perforated gummed stamp (Released 31 March 2017) - Expo Day 2 Minisheet (single stamp with rock attached).  Different stamp size and perforation from above issues/release.