Stone & Ground

What the land is made of — minerals, rock, and the ground you build on.

Key

Stops shovels or floods — watch when digging/siting

Pad, mass, drainage, road

Amendment / texture / drainage

Part of the Barito story / notable

subtitle = formula / landform type

Minerals

Barite

BaSO₄ — barium sulfate

Startlingly heavy for a dull pale rock — that dead weight is the whole mineral. Barium sulfate, ground into drilling mud to weight oil wells; the stone Barito is named for.

Quartz

SiO₂ — silica

The stubborn survivor that outlasts granite itself: silicon dioxide, hardness 7 — it scratches glass and shrugs off a knife. Most of the pale sand on the bajada is quartz and little else.

Feldspar

Pink grains in granite

The most abundant mineral in Earth's crust, and the pink in every granite boulder. Feldspar rots to clay while the quartz beside it survives as sand, the split that makes the desert's soil.

Mica

Flaky, shiny flecks

The desert's glitter and its oldest false gold — really granite coming apart. Sheet-silicate minerals that peel into thin, springy, near-transparent films under a fingernail.

Gypsum

CaSO₄·2H₂O — soft white

The softest common stone — a fingernail marks it, Mohs 2. Hydrous calcium sulfate: clear selenite, silky satin spar, or a sand-filled desert rose weathering out of a clay cutbank.

Rock Types

Granite & decomposed granite

Igneous — the ranges & the 'DG'

The mountain caught mid-crumble: cooled slow and deep, so its quartz and feldspar grew into big visible crystals — and now it sheds them grain by grain into the gritty 'DG' underfoot.

Basalt

Dark volcanic rock

A dark, dense, fine-grained lava rock with no crystals you can see. That blankness is the tell: it froze fast at the surface, where granite cooled slow and deep.

Volcanic cinder / scoria

Red, porous — 'lava rock'

A dark volcanic rock so full of frozen gas bubbles it is startlingly light and rough. The holes are the tell: it is basalt that erupted frothy. Cinder and scoria are the same thing.

Ground & Crust

Caliche

CaCO₃ hardpan layer

The pale hardpan a shovel and a post auger both hit. Rain carries calcium down but can't flush it out, cementing a layer at the exact depth the water reaches: a rain gauge frozen in the ground.

Desert pavement

Gravel-armored surface

The stones were there first: wind-blown dust sifts down beneath them and lifts the mosaic. Tens of thousands of years to set, and a tire scar that won't re-armor in a lifetime.

Desert varnish

Manganese / iron coating

The dark sheen on long-sitting desert rock isn't rust from the stone — it's dust from the sky, manganese and clay pinned on over millennia. Snap one open: the inside is pale.

Landforms

Bajada

Coalesced alluvial slope

It reads as flat ground and isn't — a bajada is a gentle slope of merged alluvial fans, sorted coarse-to-fine by flash floods. Learn the tilt and you can read where the water goes.

Wash / arroyo

Dry channel — flash-flood path

From wetter country a wash reads as a river that failed. It isn't — it's the desert's plumbing, dry between floods, and the green thread where the country keeps its life.

Playa

Dry-lake silt flat

The dead-flat, cracked clay floor at the bottom of a closed basin — a dry lake that briefly floods, then evaporates to hardpan and salt. It is where the bajada's finest dust ends up.

Soil

Soil texture: sand / silt / clay

The jar test — know your dirt

Desert ground is never just sand: it's sand, silt, and clay over caliche, and the little clay fraction is what cracks the surface and sets it brick-hard. A jar of water reads the mix.