Moderately Included — Mid-Range Clarity Grade for Coloured Stones
Moderately Included — Mid-Range Clarity Grade for Coloured Stones
Trade abbreviation MI, denoting eye-visible inclusions that affect appearance but not function
Moderately included, abbreviated MI in trade shorthand, is a clarity grade applied to coloured gemstones indicating the presence of inclusions that are easily visible to the unaided eye at normal viewing distances. The grade sits in the middle of the trade clarity scale, between slightly included (SI) and heavily included (HI), and is widely used in dealer-to-dealer communication and in some laboratory and certificate vocabulary. For buyers, MI denotes a stone that is visibly included but still functional and attractive, with the inclusions affecting transparency or brilliance to a noticeable but not overwhelming extent.
The trade clarity scale for coloured stones
Unlike diamond clarity, which has a globally standardised eleven-point GIA scale, coloured-stone clarity is graded by descriptive language and trade shorthand rather than a single universal scale. The most common trade scale runs from loupe-clean (LC) at the top, through eye-clean (EC), slightly included (SI), moderately included (MI), heavily included (HI), and severely included (SVI). Some grading reports prefer the language clean, very slightly included, slightly included, moderately included, heavily included.
The reason coloured stones do not use a unified scale is that different gem species have different normal ranges of clarity. An eye-clean emerald is rare and prized; an eye-clean aquamarine is common and unremarkable. GIA accordingly groups coloured stones into Type I, II, and III based on the typical clarity of the species, and the trade vocabulary applies within those expectations.
What MI means in practice
An MI stone shows inclusions that are easy to see at arm's length without a loupe. Common features in this grade include eye-visible crystal inclusions, healed and partially healed fissures, growth zones, milky areas, and clouds of finer inclusions sufficient in extent to reduce transparency. The inclusions remain restricted to portions of the stone rather than dominating it, and the stone retains usable face-up appearance and reasonable brilliance.
For most coloured-stone varieties, MI represents the lower bound of what the trade considers commercial fine jewellery quality. Below MI, in the HI and SVI ranges, stones are typically routed toward less demanding applications: bead strands, larger calibrated commercial goods, or industrial use.
Value implications
Clarity is a meaningful but variable price driver in coloured stones. For Type II and III species, where eye-visible inclusions are normal, the gap between MI and SI is modest. For Type I species — aquamarine, blue topaz, the kunzite varieties of spodumene — eye-visible inclusions are unusual and the price impact is more severe. For ruby, sapphire, and emerald, the value of clarity should always be weighed against colour: a moderately included ruby with fine pigeon-blood colour can be worth several times more than a clean ruby with washed-out colour. Clarity matters; colour matters more.
Inclusions as origin and authenticity evidence
Inclusions are not only flaws to be discounted; they are also the gemmologist's most reliable evidence of natural origin and, in many cases, geographic provenance. The mica platelets and calcite of Mogok ruby, the tubular three-phase inclusions of Colombian emerald, and the negative crystals and silk of Ceylon sapphire are all features that confirm what a stone is and where it came from. A moderately included natural stone with diagnostic inclusions can be worth substantially more than a cleaner synthetic equivalent for exactly this reason. See also: eye-clean; slightly included; heavily included.