Toolchest · Datasheet

Accumath Toolchest — Rocks Dataset: Notes

Dataset file: accumath-rocks.csv Compiled: 2026-10-20 Rows: 52 (20 igneous, 19 sedimentary, 13 metamorphic)

What this dataset is

A classification-level reference for common rock types: what each rock is, what it formed from, its texture, its principal minerals, its typical color, and — only where a published geotechnical table provides one — a typical uniaxial compressive strength (UCS) range and a density range. Every entry is a published fact taken from the sources listed below and named in each row's source column. Nothing in this file was estimated, interpolated, or narrowed from a wider published range.

Classification basis

• Igneous rocks are classified by silica content / mineral composition (felsic > intermediate > mafic > ultramafic) and by texture, which records cooling history: intrusive (plutonic) rocks cooled slowly at depth and are coarse-grained (phaneritic); extrusive (volcanic) rocks cooled rapidly at the surface and are fine-grained (aphanitic), glassy, vesicular, or pyroclastic. Intrusive/extrusive equivalent pairs share a melt composition: granite↔rhyolite, granodiorite↔dacite, diorite↔andesite, gabbro↔basalt. Grain-size classes used here follow the EarthSci.org identification scale (igneous: fine <1 mm, medium 1–5 mm, coarse 5–20 mm, very coarse >20 mm).
• Sedimentary rocks are classified by origin and grain size/composition: clastic rocks follow the size sequence conglomerate/breccia (gravel, >2 mm, rounded vs angular) → sandstone (sand) → siltstone (silt) → mudstone/shale (clay; shale is the fissile member); chemical rocks precipitate from solution (limestone, dolomite/dolostone, chert, rock salt, rock gypsum, travertine); organic/biochemical rocks accumulate plant or skeletal debris (coal series, oil shale, coquina, chalk). Sandstones are further classified by composition: quartz arenite (>95% quartz), arkose (>25% feldspar).
• Metamorphic rocks are classified by texture — foliated (slaty → phyllitic → schistose → gneissic banding, in order of increasing grade) vs non-foliated — and by protolith. The pelitic series shale → slate → phyllite → schist → gneiss → migmatite is one protolith carried through increasing temperature and pressure. Protolith assignments follow the LibreTexts introductory geology laboratory manual (Table 11.1) and the Geophile protolith/grade chart (basalt → greenschist at low grade, amphibolite/eclogite at high grade; sandstone → quartzite; limestone → marble; bituminous coal → anthracite).

Strength (UCS) values — method and limits

UCS cells are filled only where a published table gives a range. Two tables were used, and each filled row's note says which:

1. Direct per-rock ranges — ScienceDirect Topics, "Rock Strength" overview, Table 12.4 (uniaxial compressive strength ranges for geological-storage rock types): basalt 50–150 MPa, limestone 50–100 MPa, sandstone 20–100 MPa, siltstone 40–100 MPa, shale 20–200 MPa.
2. Field-estimate grade bands — Hoek & Brown, Practical Estimates of Rock Mass Strength, Table 1 ("Field estimates of uniaxial compressive strength", grades after Brown 1981). This table does not give a range per rock; it gives a UCS band per grade and lists example rocks in each grade: R6 extremely strong >250 MPa (fresh basalt, chert, diabase, gneiss, granite, quartzite); R5 very strong 100–250 MPa (amphibolite, sandstone, basalt, gabbro, gneiss, granodiorite, limestone, marble, rhyolite, tuff); R4 strong 50–100 MPa (limestone, marble, phyllite, sandstone, schist, shale); R3 medium strong 25–50 MPa (claystone, coal, schist, shale, siltstone); R2 weak 5–25 MPa (chalk, rocksalt, potash). Where a rock appears in exactly one grade, that grade's band is carried. Where it appears in two adjacent grades, the union band is carried (marble 50–250; schist 25–100; gneiss ">100", listed in both R5 and R6). Where the direct table (1) also covers the rock, the direct range is used instead (this affects basalt, limestone, sandstone, siltstone, shale).

Known conflicts, left visible rather than resolved silently:

• Basalt: the direct table gives 50–150 MPa; the field grades place basalt in R5 (100–250) and fresh basalt in R6 (>250). The dataset carries the direct range and notes the discrepancy in the basalt row.
• Tuff: Hoek & Brown list tuff as an R5 example, while a published standards-comparison classification (Kamieński & Skalmowski, via bibliotekanauki.pl) classes tuffs as very low strength (<40 MPa). Welded and unwelded tuffs differ enormously, the sources conflict, so the tuff UCS cell is blank.

All other UCS cells are blank because no table used here publishes a range for that rock type. These are intact-rock, laboratory/field-estimate magnitudes — not rock-mass design values.

Density values — method and limits

Density ranges are carried only for the nine rock types in the one published range table used: LibreTexts / ChemEd DL, "Density of Rocks and Soils", Table 1 — amphibolite 2.79–3.14, dolomite 2.72–2.84, gneiss 2.59–2.84, limestone 1.55–2.75, marble 2.67–2.75, schist 2.73–3.19, shale 2.06–2.67, slate 2.72–2.84 g/cm³. All other density cells are blank: no comparably published range table covering the remaining rock types was reachable, and single "typical" point values were not substituted for ranges.

The standing caveat (read before using any number)

A rock name is a family, not a material specification. Two rocks both correctly named "granite" or "sandstone" can differ severalfold in strength and density depending on the deposit: mineral proportions, grain size, cement, porosity, fracturing, and weathering state all move the properties, and foliated rocks (foliation-parallel vs foliation-normal loading in slates, schists and phyllites can differ by a factor of about 5, per the Salcedo results discussed by Hoek & Brown). The ranges here are orientation values for education and preliminary work. Any engineering use requires testing samples from the actual deposit — the same rule the Toolchest applies to concrete.

Coverage notes and deliberate exclusions

• Komatiite is included: its definition was verified against the Geoscience Canada komatiite review and the Wikipedia summary of the same literature (ultramafic lava crystallized from melt of ≥18 wt% MgO, typically spinifex-textured, essentially Archean).
• Porphyry is included as a texture reference row, flagged in its notes cell: porphyritic texture is not a composition, and correct usage pairs it with a compositional name (granite porphyry, andesite porphyry).
• Anthracite appears once, with the coal series in the sedimentary block, flagged as the metamorphosed end member (protolith bituminous coal, per LibreTexts Table 11.1) rather than duplicated as a metamorphic row.
• Oolitic limestone is folded into the limestone row (ooids are named in its composition) rather than given a separate row; greenschist is given its own row as the named low-grade product of mafic protoliths; serpentinite stands alone rather than as a note under schist.
• Rocks not in the assigned scope (e.g. greywacke, laterite, bauxite, metaconglomerate, granulite, blueschist) were left out deliberately.

Sources (all opened and read during compilation)

• Geology Science — rock identification chart and per-rock articles (geologyscience.com): identification features, colors, granite modal composition and engineering remarks, kimberlite composition and occurrence.
• Igneous rock properties table, university lecture deck (slideshare.net): texture, composition, intrusive/extrusive equivalents, felsic–mafic grouping for the common igneous rocks.
• Igneous classification by silica content, geology lecture notes (scribd.com): ultramafic/basic/intermediate/acid silica classes.
• EarthSci.org, Rock Identification Basics (earthsci.org): rock origin definitions and the grain-size scales for all three classes.
• University of Iowa instructional resources, Sedimentary Rocks list: sedimentary rock definitions (conglomerate, breccia, sandstone, shale, arkose, tufa/travertine, gypsum, limestone, dolomite, fossil limestone/coquina, rock salt, chalk, oil shale, bituminous coal).
• LSU geology course pages, sandstone classification (geol.lsu.edu) and sedimentary nomenclature course material (brainscape.com): quartz arenite (>95% quartz) and arkose (>25% feldspar) compositional definitions, chert.
• LibreTexts, Laboratory Manual for Introductory Geology, §11.3 Table 11.1 and §6.2/§8.2 identification tables (geo.libretexts.org): metamorphic textures, compositions and protoliths.
• The Geophile Pages, metamorphic protolith/grade chart (geophile.net); CliffsNotes, Metamorphic Rock Types (cliffsnotes.com): grade progressions, greenschist/amphibolite/eclogite from basalt, serpentinite, migmatite.
• UBC EOSC laboratory notes (eoas.ubc.ca): kimberlite macrocryst mineralogy; eclogite = garnet + omphacitic clinopyroxene, no plagioclase.
• Dunite (en.wikipedia.org); Komatiites review, Geoscience Canada (thefreelibrary.com); Testbook geology explanations (testbook.com): soapstone (talc-dominated, from peridotite/dunite).
• Hoek, E. & Brown, E.T., Practical Estimates of Rock Mass Strength, Table 1 (hosted at geoplanning.it): UCS field-estimate grade bands and example rocks.
• ScienceDirect Topics, Rock Strength overview, Table 12.4: direct UCS ranges for basalt, limestone, sandstone, siltstone, shale.
• LibreTexts / ChemEd DL, Density of Rocks and Soils (chem.libretexts.org): the density ranges carried in the dataset.

All sources are openly published educational or professional references; US government material (the classification framework taught by USGS-style educational geology) is public domain, and the remaining values are published facts recorded with attribution, per the Toolchest legal basis.